Potential Risk Factors for the Development of Self-Injurious Behavior among Infants at Risk for Autism Spectrum Disorder
J Autism Dev Disord
Potential Risk Factors for the Development of Self-Injurious Behavior among Infants at Risk for Autism Spectrum Disorder
Adele F. Dimian 0 1 2 3 4 5 6 7
Kelly N. Botteron 0 1 2 3 4 5 6 7
Stephen R. Dager 0 1 2 3 4 5 6 7
Jed T. Elison 0 1 2 3 4 5 6 7
Annette M. Estes 0 1 2 3 4 5 6 7
John R. Pruett Jr. 0 1 2 3 4 5 6 7
Robert T. Schultz 0 1 2 3 4 5 6 7
Lonnie Zwaigenbaum 0 1 2 3 4 5 6 7
Joseph Piven 0 1 2 3 4 5 6 7
Jason J. Wolff 0 1 2 3 4 5 6 7
The IBIS Network 0 1 2 3 4 5 6 7
0 Department of Radiology, University of Washington , Seattle, WA , USA
1 Department of Psychiatry, Washington University in St. Louis , St. Louis, MO , USA
2 Department of Educational Psychology, University of Minnesota , 56 East River Rd., Minneapolis, MN 55455 , USA
3 Department of Psychiatry, University of North Carolina at Chapel Hill , Chapel Hill, NC , USA
4 Department of Pediatrics, University of Alberta , Edmonton, AB , Canada
5 Center for Autism Research, Children's Hospital of Philadelphia , Philadelphia, PA , USA
6 Department of Speech and Hearing Sciences, University of Washington , Seattle, WA , USA
7 Institute of Child Development, University of Minnesota , Minneapolis, MN , USA
Prevalence of self-injurious behavior (SIB) is as high as 50% among children with autism spectrum disorder (ASD). Identification of risk factors for the development of SIB is critical to early intervention and prevention. However, there is little empirical research utilizing a prospective design to identify early risk factors for SIB. The purpose of this study was to evaluate behavioral characteristics predicting SIB at age 2 years among 235 infants at high familial risk for ASD. Logistic regression results indicated that presence of SIB or proto-SIB and lower developmental functioning at age 12 months significantly predicted SIB at 24 months. A pattern of persistent SIB over this period was Joseph Piven and Jason J. Wolff have contributed equally to this work.
Self-injurious behavior; Repetitive behavior; Autism spectrum disorder; Risk factors; Infants
* Jason J. Wolff
Repetitive behavior is a core diagnostic feature of autism
spectrum disorder (ASD). Self-injurious behavior (SIB)
is a form of repetitive motor behavior that is both
selfdirected and has the potential to result in tissue damage
(Lewis and Bodfish 1998; Tate and Baroff 1966).
Examples of SIB topographies include head hitting, head
banging, skin picking and pinching, hair pulling, and self-biting
(Rojahn et al. 2008). SIB point-prevalence estimates (i.e.,
the number of cases of SIB at one point in time divided by
the number of persons in a defined population at the same
point in time) vary widely depending on age and
diagnosis, but estimates range from 2 to 24% in community/total
population studies of individuals with intellectual
disabilities (Cooper et al. 2009). For individuals with autism
spectrum disorder (ASD), point-prevalence estimates for
SIB have been reported to be as high as 53% among
children (Baghdadli et al. 2003; Duerden et al. 2012), and 69%
among adults with the disorder (Bodfish et al. 2000). While
more rigorous epidemiological studies are needed,
existing work suggests that SIB is a relatively common behavior
disorder that occurs across the lifespan of individuals with
ASD. The deleterious effects associated with SIB, such as
risk of permanent injury and interference with the
acquisition of adaptive behaviors, can negatively impact the
quality of life of affected individuals and their families (e.g.,
Emerson 1990; Emerson et al. 2001b; Eyman and Call
1977; Symons and Thompson 1997; Taylor et al. 2011).
There are currently no established prevention
programs targeted specifically at reducing the incidence of
SIB among children with neurodevelopmental disorders
such as ASD. Although there have been promising
findings from a limited number of prevention oriented studies
utilizing functional communication training (e.g., Fahmie
et al. 2016; Luszynski and Hanley 2013; Reeve and Carr
2000; Richman 2008), there is a need to first clarify the
clinically-relevant risk factors for the development and
persistence of SIB. The extant literature on putative risk
factors and associated variables with SIB varies greatly in
terms of the methodology, measurement tools, and the
target populations and ages investigated (Furniss and Biswas
2012; MacLean et al. 2010; McClintock et al. 2003; Rojahn
et al. 2008). The number of observational studies to date
specific to SIB is impressive; their findings, however, can
be difficult to generalize across diagnostic categories (e.g.,
etiologically defined disorders, ASD, idiopathic intellectual
disability, and at-risk/ developmental delay groups) and age
groups in particular (McClintock et al. 2003).
Previous research on adults with a diagnosis of ASD
suggests that SIB may be more prevalent (Richards et al.
2012) and of greater severity (Bodfish et al. 2000) in
comparison to individuals with intellectual disabilities. When it
comes to identified risk factors (i.e., a factor that directly
increases the probability of SIB occurring and is part of
a causal chain) and risk markers (i.e., an attribute that is
associated with increased probability of SIB, but is not
necessarily causal), there are disparate findings and mostly
data on the latter (Burt 2001). In a meta-analysis conducted
by McClintock et al. (2003), common risk markers for SIB
among various samples of children and adults with
intellectual disabilities included an autism diagnosis, severity
of autism, level of intellectual functioning,
communication deficits, and the presence of certain syndromic
neurodevelopmental disorders (e.g., Lesch-Nyhan syndrome).
Among2008 the few longitudinal studies of
individuals with intellectual disabilities, the three most reported
risk markers for the persistence of SIB in adolescents and
adults are lower receptive and expressive language
(Chadwick et al. 2008; Emerson et al. 2001a; Kiernan and Alborz
1996; Nøttestad and Linaker 2001; Schroeder et al. 1978),
lower daily living skills and adaptive behavior (Chadwick
et al. 2008; Emerson et al. 2001a; Kiernan and Alborz
1996; Nøttestad and Linaker 2001), and intellectual
disability (Cooper et al. 2009; Nøttestad and Linaker 2001;
Schroeder et al. 1978).
The potential risk factors and markers specific to the
early development of SIB, however, have been examined
primarily cross-sectionally and retrospectively (e.g.,
Fodstad et al. 2012). Berkson et al. (2001) were among the first
to follow a group of young children with developmental
disabilities who were receiving birth to three early
intervention services (3–40 months old). The group reported that
onset of SIB occurred on average at age 16 months.
Similarly, Kurtz et al. (2003) and Richman and Lindauer (2005)
reported that both SIB and proto-injurious SIB (proto-SIB;
topographies similar to SIB that do not cause tissue
damage) emerge before or at 25 months of age. Proto-SIB has
been identified as a potential risk marker for the emergence
of SIB (Furniss and Biswas 2012; Petty et al. 2009;
Richman and Lindauer 2005; Symons et al. 2005). Repetitive
rhythmic motor stereotypies, such as body rocking and
hand flapping, have also been considered as a potential
behavioral precursor to SIB (Baumeister and Forehand
1973; Rojahn et al. 2015). Through extended contact with
the social environment, certain motor stereotypies may be
shaped into topographies of SIB and possibly become
sensitive to social reinforcement (Guess and Carr 1991;
Kennedy 2002; Oliver et al. 2005). Empirical studies
addressing this model of SIB development are limited and findings
overall have been mixed (Furniss and Biswas 2012). Causal
relationship aside, there is evidence that motor stereotypy
is associated with SIB (Barnard-Brak et al. 2015; Oliver
et al. 2012; Petty et al. 2009; Rojahn et al. 2012) and may
predict its occurrence (Barnard-Brak et al. 2015; Richman
et al. 2012; Rojahn et al. 2015).
Prospective, longitudinal cohort designs are essential
for identifying predictive temporal relations and provide
stronger evidence for causal inferences than
retrospective cohort and cross-sectional designs (Aschengrau and
Seage 2014). Only two sets of prospective cohort studies
and one direct observation study have investigated early
SIB among young children at risk for developmental delay
(Rojahn et al. 2015; Schroeder et al. 2014) and with
developmental disabilities (Berkson 2002; Berkson et al. 2001;
Richman and Lindauer 2005) that included some children
with ASD. With a sample of young children at risk for a
behavior disorder such as aggression or SIB from Peru
(n = 180; age = 4–48 months), Schroeder et al. (2014)
examined potential risk factors across three time points.
Results indicated that SIB varied by diagnostic group status
over time. More specifically, children screening positive for
ASD engaged in high rates of SIB at time 1 that decreased
over time, while children with Down syndrome showed
low levels of SIB at time 1 that increased modestly
thereafter. Using the same data from Schroeder et al. (2014) and
Rojahn et al. (2015) examined the relationship of motor
stereotypy to SIB over time using latent growth modeling.
The authors concluded that the best fitting model included
stereotypy as a predictor of later SIB. Berkson (2002)
examined age trends among young children receiving early
intervention services, finding that SIB emerged early on,
with certain topographies, such as head banging, appearing
first. Richman and Lindauer (2005) also examined
emerging SIB over time among young children with
developmental delay (n = 12; age = 14–32 months) using functional
analyses. Each analysis was individualized and stereotypy,
proto-SIB and SIB were targeted and followed over time.
The results indicated that the topography and function of
the target behavior stayed the same for most of the
participants. While most participants in that study showed both
motor stereotypies and proto-SIB at study entry, the latter
behavior changed over time to include new topographies or
to increase in severity (causing tissue damage) for 5 of 12
children. Taken together, SIB onset patterns appear to vary
dynamically over time in relation to diagnostic status and to
other forms of repetitive behavior.
To date, there are no prospective cohort studies of SIB
among young children at high familial risk for ASD, who
are defined as such by virtue of having an older sibling with
the disorder, during the first years of life. Because SIB is an
early-emerging behavioral disorder associated with autism
and developmental delay (Dominick et al. 2007; Duerden
et al. 2012), the focus of the current study was to downward
extend the literature on potential risk factors for SIB
development and persistence to infants at high risk for ASD.
Specifically, we examined cognitive and behavioral
characteristics at age 12 months in relation to presence or absence
of SIB at age 24 months in a longitudinal study of 235
children at familial high risk for ASD.
Study participants were from the Infant Brain
Imagining Study (IBIS), an ongoing longitudinal multisite study
of infants at high familial risk for ASD. Participants were
recruited from across the United States through research
registries, flyers, brochures, community clinics, websites,
and email blasts. Assessments were performed at one of
four clinical data collection sites including Children’s
Hospital of Philadelphia, University of North Carolina,
University of Washington, and Washington University in St.
Louis. Exclusion criteria entailed: (1) evidence of a
specific genetic condition or syndrome; (2) significant
medical or neurological condition affecting development; (3)
significant vision or hearing impairment; (4) birth weight
<2000 g or gestational age < 36 weeks; (5) significant
perinatal adversity or prenatal exposure to neurotoxins, (6)
contraindication for MRI, (7) predominant home language
other than English, (8) children who were adopted or half
siblings, (9) 1st degree relative with psychosis,
schizophrenia, or bipolar disorder, and (10) twins. Familial
highrisk status was defined by having an older sibling with a
community diagnosis of the ASD confirmed by the Autism
Diagnostic Interview-Revised (ADI-R; Lord et al. 1994)
and Social Communication Questionnaire (SCQ; Rutter
et al. 2003).
The present study included a sample of infant siblings
considered to be at high risk for ASD, for whom
cognitive and behavioral assessment batteries were completed
at 12 and 24 months of age (n = 235). The cognitive and
behavioral assessments included a parent-report measure
of repetitive and self-injurious behavior. For the purpose
of providing context, descriptive data on SIB is also
provided for a sample of low-risk control infants; however, this
group was not included in subsequent analyses given our
study aims and overall low base rate of SIB in this group
[n = 95; SIB at 24 months = 14/95 (14.7%)]. Low-risk
infants were recruited and assessed as part of the parent
study. Low-risk infants met the exclusion criteria described
above and had typically developing older siblings as
confirmed by the SCQ and no first-degree relatives with ASD
or intellectual disability. High- and low-risk infants had
complete Repetitive Behavior Scales-Revised (RBS-R) at
both 12 and 24 months. Subgrouping of high-risk
participants on the basis of diagnostic status at age 2 was based on
clinical best-estimate using DSM-IV-TR criteria made by
experienced, licensed clinicians using all available clinical
and developmental assessment data, with confirmation by a
second senior clinician blind to risk and diagnostic status.
Study procedures were approved by institutional review at
each clinical assessment site with informed consent
documented for all participants.
The Repetitive Behavior Scales—Revised (RBS-R;
Bodfish et al. 2000) is a parent or caregiver rated measure of
restricted and repetitive behaviors comprised of 43 discrete
behavioral topographies. The RBS-R provides scores for
total repetitive behavior as well as for six subtypes thereof.
RBS-R measures of interest to the present study were
inventories of self-injurious behavior (SIB)
and stereotypical motor. The SIB subscale was the primary dependent
variable and was used as a binary grouping variable (SIB
or no SIB) based on the presence or absence of any SIB
item endorsed by caregivers at 24 months. The SIB and
stereotypical motor subscales were also used to catalogue
the number and type of these behaviors at ages 12 and
24 months. The RBS-R, including our subscales of
interest, captures individual differences in behavior among
toddlers at high-risk for ASD (Wolff et al. 2014) and has been
independently validated for use in young children (Mirenda
et al. 2010).
The Autism Diagnostic Observation Schedule (ADOS;
Lord et al. 2000) is a semi-structured diagnostic assessment
designed to probe for symptoms associated with ASD. The
ADOS was used to generate a standardized symptom
severity score (Gotham et al. 2009) as well as domain scores for
repetitive behavior and social affective symptoms.
Assessment data from the ADOS also contributed to the
determination of diagnostic classification. While updates have
been made to the ADOS subsequent to the initiation of our
longitudinal study, use of the ADOS-G was maintained to
ensure consistency across subjects and time.
The Mullen Scales of Early Learning (MSEL; Mullen
1995) is a standardized developmental assessment designed
for children ages 0–68 months. The Early Learning
Composite (ELC) score, an index of overall cognitive and
behavioral development, was used to provide an estimate
of overall developmental quotient. The ELC is a standard
score with M = 100, SD = 15. Subscales from the MSEL
were used in secondary analyses and included expressive
and receptive language, fine and gross motor, and visual
reception. These subscales yield T-scores with M = 50,
SD = 10. Separate non-verbal and verbal developmental
quotients were also calculated based on age-equivalent
Vineland Adaptive Behavior Scales-II The Vineland
(Sparrow et al. 2005) is a standardized and
norm-referenced assessment of adaptive function based on a
semistructured parent interview. The Vineland provides an
Adaptive Behavior Composite (ABC) score as well as
indexes of adaptive function in each of four subdomains,
including socialization, which indexes interpersonal
relationships, play and leisure skills, and interpersonal coping
skills. This subdomain was of specific interest given a
previously observed inverse relationship between
socialization skill and repetitive behavior in toddlers who developed
ASD (Wolff et al. 2014). Although daily living skills have
been previously linked to SIB in older individuals
(Kiernan and Alborz 1996; Emerson et al. 2001b; Nøttestad and
Linaker 2001; Chadwick et al. 2008), this Vineland
subdomain was not examined given questionable relevance to
toddlerhood. The Vineland ABC and Socialization scores
are standardized, M = 100, SD = 15.
To explore the relationship between the variables of
interest and the outcome (presence or absence of SIB as defined
by the RBS-R), descriptive and correlational analyses were
conducted to characterize the high risk infants included in
this study. Point-prevalence (number of participants with
SIB, new and preexisting, at one time point divided by the
total sample), cumulative incidence (number of participants
who developed SIB in the specific time period divided by
the number of participants at risk of developing SIB at
the beginning of the period), and relative risk (cumulative
incidence in the exposed group, i.e. group with the
potential risk factor, divided by the cumulative incidence in the
unexposed group) estimates were calculated (Aschengrau
and Seage 2014). Next, a series of logistic regression
models were fitted to test which psychosocial variables (based
on the extant literature) at 12 months (time 1) were
predictive of parent-endorsed SIB (SIB or no SIB) at 24 months
(time 2). Odds ratios were calculated based on these
models for each predictor variable tested. Bootstrap sampling
with replacement (B = 1000) was used to generate
confidence interval estimates. Finally, secondary analyses using
one-way ANOVA were conducted to further characterize
and explore possible group-level differences in select
cognitive and behavioral features between participants based
on SIB status at times 1 and 2 (persistent SIB, incident SIB,
transient SIB, and no SIB). This included MSEL composite
and subscale scores and Vineland adaptive composite and
socialization score. Post-hoc pairwise comparisons were
performed following the omnibus ANOVA and corrected
using the Tukey method.
The primary study sample of high risk infants included
62.6% males and was 87.3% white. The mean age at 12 and
24 months assessment dates were 12.5 (SD = 0.6) and 24.8
(SD = 1.5) months, respectively (see Table 1 for
descriptive and demographic information). Of the 235 high risk
infants, 47 (20%) met clinical best-estimate criteria for
ASD at age 24 months (combined autistic disorder or
pervasive developmental disorder, not otherwise specified).
At age 12 months, the point prevalence estimate for
children who engaged in SIB was approximately 39%. In
comparison, at age 24 months, the point prevalence estimate
for children who exhibited SIB was 32%. Of the children
whose parents endorsed at least one topography of SIB at
12 months, 48% persisted in engaging in SIB at 24 months.
Incidence and Persistence
At 24 months of age, there were 31 incident cases of SIB
(i.e., new cases of SIB at 24 months). The cumulative
incidence estimate (i.e., absolute risk) was 0.22 over 12
months. Among the children who engaged in SIB at both
12 and 24 months, 47% decreased in the total number of
topographies of SIB (i.e., total SIB items endorsed), while
28% were reported to have an increase in number of
topographies. The remaining 26% of children who persisted in
SIB from 12 to 24 months were reported to have the same
Table 1 Descriptive and
Total sample (n = 235)
overall number of topographies of behavior at both time
points. For low risk infants, cumulative incidence was 0.08
and persistence of SIB from 12 to 24 months was
approximately 6%. Cumulative incidence and persistence were
significantly lower for low risk infants in comparison to
high-risk infants (Fisher’s exact test; p < .001 and p = .003,
up (transient n = 48), and children who had no SIB at either
time point (no SIB n = 112). There was a significant
relationship between a diagnostic group status and SIB status,
X 2 (3, n = 235) = 10.1, p = .02. Children meeting criteria
for ASD at age 24 months constituted 32% of the
persistent group, 36% of the incident group, 19% of the transient
group, and 14% of the no SIB group.
One or more topographies of SIB were endorsed at either
time point for 74% of participants with an ASD diagnosis
and 47% for those without. A relative risk estimate was
calculated comparing participants who received a diagnosis
at 24 months compared to those who did not. The results
indicated that the risk of engaging in SIB at 24 months was
1.85 times higher among children who were later
diagnosed with ASD compared to children who did not receive
ASD Diagnosis by SIB Group
A chi-square test was performed to evaluate if a
diagnosis of ASD significantly differed by SIB status. The four
groups compared were children who engaged in SIB at
both 12 and 24 months (persistent n = 44), children who
started engaging in SIB at 24 months (incident n = 31),
children who engaged in SIB at 12 months but not at follow
SIB Subscale Items
At 12 months, participants engaged in hitting against a
surface and pulling skin or hair the most (Fig. 1). The least
endorsed item within the SIB subscale at 12 months was
skin picking. Caregivers also endorsed hitting self against
a surface the most at 24 months. The least endorsed item at
24 months was hits self with an object. SIB only increased
in terms of item endorsement for bites self and inserts
finger or object. Overall, all other forms decreased at 24
months, with pulling hair and/or skin decreasing the most.
The SIB items endorsed were also compared at 24
months between participants who engaged in SIB at both
time points (i.e., persistent cases) and those who just started
engaging in SIB at Time 2 (i.e., incident cases) (Fig. 2). A
similar pattern was observed at 24 months with the both
the incident and persistent SIB cases engaging in hits body
against a surface the most, with 39 and 49%, respectively.
The least endorsed item for both types of cases was hits
self with object, (7% incident and 12% persistent). Overall,
Fig. 1 Caregiver endorsement
of items on RBS-R stereotyped
and self-injurious behavior
Fig. 2 Self-injurious behavior
items endorsed by caregivers at
24 months among incident cases
(n = 31) and persistent cases
(n = 43)
Stereotyped Item Endorsed
RBS-R SIB Subscale
Hits self Skin
with object picking
Bites self Pulls skin/ Hits self Inserts
hair with body finger or
SIB Item Endorsed
RBS-R Stereotyped Subscale
RBS-R SIB Subscale Items
proportions of reported topographies on the SIB subscale
were relatively similar between incident and persistent
Stereotyped Behavior Subscale Items
Figure 1 also displays the topographies endorsed
(itemlevel RBS-R data) for stereotyped behavior on the RBS-R.
At 12 months, caregivers endorsed hand finger stereotyped
behavior the most, and locomotion the least. At 24 months
for the stereotyped behavior subscale, caregivers endorsed
repetitive object usage the most, and repetitive head
movement the least. Overall, topographies of stereotyped
behaviors that decreased from 12 to 24 months at assessment
time included head, whole body, and hand finger.
Conversely, topographies that increased in terms of caregiver
endorsement at 24 months were locomotion, sensory, and
Four logistic regression models (Table 2) were fitted to
examine which characteristics significantly predicted
SIB at 24 months among all high-risk infants. The first
model included all variables of interest, based on the
literature, including sex, MSEL ELC (developmental
quotient), Vineland ABC (adaptive behavior), and endorsed
SIB and stereotyped behavior items from the RBS-R. Of
these predictors, only MSEL ELC score and SIB at 12
months were statistically significant predictors of SIB at
24 months at (X2 = 35.83, df = 5, p < 0.001). Subsequent
to this result, Model B was fit with MSEL ELC, endorsed
items of SIB, and endorsed items of stereotyped behavior
at age 12 months. In Model B, again only MSEL ELC and
SIB endorsement were statistically significant predictors.
Table 2 Unadjusted odds
ratios with 95% confidence
intervals between psychosocial
characteristics at 12 months and
SIB at 24 months
For Model C, we tested only MSEL ELC and stereotyped
behavior in relation to later SIB. Both factors were
statistically significant. For a final Model D, we tested the
contribution of MSEL ELC and SIB items endorsed. Both
predictors were statistically significant and model fit was
similar to that of Models A and B and superior to Model
C. Overall, the results of logistic regression analysis
indicated that for participants who exhibited SIB at 12 months,
the odds of engaging in SIB at 24 months was between
75–92%. Consistent across models, the odds of SIB at Time
2 decreased by 3% for each unit increase in the MSEL ELC
score. Goodness-of-fit was relatively consistent across
Models A, B, and D, with R2pseudo = 0.21 for A and B, and
R2pseudo = 0.19 for Model D. Goodness-of-fit for Model C,
which included MSEL ELC and stereotyped behavior, was
less robust with R2pseudo = 0.13.
Table 3 displays the results of a one-way ANOVA to test
mean differences in MSEL ELC and subscale scores and
select Vineland scores between children who persisted in
engaging in SIB from 12 to 24 months of age, those who
did not (i.e., no SIB or transient), and incident cases of SIB
at 24 months. There were statistically significant mean
differences between groups for the MSEL composite score as
well as receptive language, gross motor, and visual
reception subscales (see Table 3). For the Vineland, there were
statistically significant mean differences between groups
for both adaptive composite score and socialization scores.
Post-hoc analyses corrected for multiple comparisons
suggested that groups with no or transient SIB (i.e., SIB
at 12 months but not at 24 months) did not differ
significantly from one another and were characterized by higher
scores across MSEL and Vineland measures relative to the
RBS-R SIB endorsed
RBS-R stereotyped endorsed
Vineland adaptive behavior composite
MSEL ELC mullen early learning composite, RBS-R repetitive behavior scale, revised
*p < 0.05, **p < 0.01, ***p < 0.001
persistent and incident SIB groups. Children in the
persistent SIB group had the lowest MSEL and Vineland scores
overall, and their scores were significantly lower than
those of the transient and no-SIB groups on the majority
of MSEL and Vineland measures. The incident SIB group
was intermediate to the persistent and transient SIB groups.
The purpose of this study was to evaluate characteristics at
age 12 months that predicted self-injurious behavior (SIB)
at age 24 months among infants at familial high risk for
ASD. We were particularly interested in downward
extending findings from the extant literature on SIB in order to
test putative risk markers for later emerging SIB. In the
most parsimonious model, we found that SIB at 12 months
in an infant’s repertoire and lower
developmental/intellectual functioning significantly predicted the emergence
and/or persistence of SIB at age 24 months among infants
at high risk. Contrary to some of the extant literature on
potential risk markers (e.g. Emerson et al. 2001b; Rojahn
et al. 2015), we did not find strong evidence for motor
stereotypy as a predictor of SIB. Indeed, stereotypy was only
modestly predictive of later SIB in a model which did not
account for early manifestations of SIB-related
topographies. This may be due to how highly correlated SIB and
stereotyped behavior are or may indicate that specific
topographies of stereotypy, versus stereotypy in general,
are associated with SIB. For example, in a cross-sectional
sample of 1871 children and adults with intellectual
disabilities, Barnard-Brak et al. (2015) found that stereotyped
behavior was a strong predictor of SIB for 69% of
participants but not for the remaining 31%. Their results also
indicated that specific topographies of stereotypy (yelling and
body rocking) may predict specific forms of SIB, versus a
more general relationship between these classes of
behavior. Alternatively, the present findings may indicate that the
relationship between stereotypy and SIB qualitatively
differs for children at-risk for ASD during early development.
With regard to the relationship of SIB to stereotypy,
there are two issues which merit consideration. First, there
is evidence that, despite some topographical similarity,
SIB and stereotypy may be distinct phenomenon in terms
of both behavior (Bishop et al. 2013; Mirenda et al. 2010;
Richler et al. 2007; Wolff et al. 2016) and underlying
neurobiology (Wolff et al. 2013). Second, as opposed to
stereotypies in general, it is feasible that the SIB topographies
reported (i.e., endorsed SIB items) among our sample of
toddlers at risk for ASD more closely reflect proto-SIB
as originally conceived (Berkson et al. 2001; Richman
and Lindauer 2005). That is, stereotyped motor
behaviors which have the potential to cause tissue damage (e.g.,
light head or leg slapping, banging of objects against self,
or hand mouthing) but that have not yet risen to a pivotal
level of severity or concern (e.g., audible self-directed
hitting that produces red marks or bruises; hand mouthing that
results in chapped hands or other tissue damage).
While our sample overall was relatively typically
developing as indicated by mean cognitive and adaptive
behavior scores, a substantial minority will be characterized
by atypical development in the form of ASD or a related
neurodevelopmental or psychiatric disorder by school age
(Miller et al. 2016). At age 24 months, approximately 20%
of high-risk children met diagnostic criteria for ASD. SIB
occurred at a higher rate among children receiving a
diagnosis of ASD, but was not exclusive to this subset of
highrisk infants. The relative risk of a child with ASD
engaging in SIB at 24 months was almost two-fold that of a child
without a diagnosis. These data are consistent with
previous work and suggest that SIB emerges early in life, can
be persistent, and is prevalent among children with ASD
(e.g., Baghdadli et al. 2008; Berkson et al. 2001; Schroeder
et al. 2014). Almost half of the participants who engaged
in SIB at Time 1 persisted in engaging in SIB at follow up.
Other studies report high persistence estimates among
individuals with intellectual disabilities (Taylor et al. 2011) and
children with PDD-NOS (Baghdadli et al. 2008). Based on
these data, it is likely that once proto-injurious behavior or
SIB emerges, it may remain stable, and should be evaluated
even if it is not yet severe yet.
A strength of this study was its use of a longitudinal and
prospective cohort design, adding to a very limited
published literature using such an approach to the study SIB
among young children with or at-risk for a developmental
disability. With the prospective cohort design, we were
able to calculate the cumulative incidence of SIB (i.e., new
cases of SIB that developed over a period of time) over a
12-month period. There are very few cumulative incidence
estimates of SIB reported in the literature. Incidence
estimates are needed for the assessment of prevention trials
(i.e., the impact of the program on the incidence of SIB)
and so the inclusion of this estimate may lay the
groundwork for future research. Berkson et al. (2001) estimated
that among 39 children under the age of 40 months
receiving early intervention services for general developmental
delay, incident cases of SIB were 1.3% over 1–3 years of
follow up. Murphy et al. (1999) followed an older sample
of 614 children with intellectual disabilities (under the age
of 10 years) and reported a cumulative incidence of 3%.
Among a sample of adults with intellectual disabilities,
Cooper et al. (2009) reported a cumulative incidence of
SIB of 0.6% over 2 years of follow up (n = 651).
Measurement variability and sample characteristics likely
contribute to this range of cumulative incidence estimates. Results
from the present study pertain to a particular risk group
over a focused age interval: toddlers at familial high risk
for autism from 12 to 24 months of age. While we expect
that our findings may not generalize to other risk groups
or ages, they do provide specific targets for further study,
including the possibility of developing early intervention or
In general, the developmental progression of early SIB is
not well understood. Results from two published
cross-sectional studies and one longitudinal study suggest that head
banging is the most common early SIB topography
(Berkson et al. 2001; MacLean and Dornbush 2012; Kurtz 2012).
Hand biting and hand mouthing are also common SIB
topographies reported for young children with intellectual
and developmental disabilities (Murphy et al. 1999; Hall
et al. 2001; Richman and Lindauer 2005). Within the
present sample, changes in SIB topographies (endorsed items
on the SIB subscale) were observed from 12 to 24 months.
Hitting self against surface (e.g., head banging) was the
most commonly endorsed topography at 12 and 24 months,
and tended to remain in the children’s repertoires across
time points and across SIB groups (incident, persistent, and
transient). Overall, a majority of the items endorsed (47%)
decreased from ages 12 to 24 months. For example, skin
and hair pulling decreased sharply over this interval. Other
forms showed an increase, as with self-biting. An early
developmental pattern of decreasing SIB, function
notwithstanding, has been reported in typically developing children
among whom such behaviors are relatively common and
often associated with tantrums (Berkson and Tupa 2000;
Hoch et al. 2015). It may be that stability of SIB into
toddlerhood is a clinically relevant feature that merits specific
consideration in future prospective research (Emerson et al.
2001a). Given that those with a diagnosis of ASD were
almost twice as likely to engage in SIB at 24 months than
those who did not receive a diagnosis, it may be prudent
to monitor early repetitive behavior in general and SIB in
particular closely during the first years of life for children
who are at high risk.
In an attempt to further elucidate risk markers
predicting SIB within our sample, secondary analyses focused on
MSEL subscales and the Vineland were performed. We
examined group-level differences in cognitive and
behavioral features among children based on whether their SIB
from 12 to 24 months was persistent, transient, or incident,
as well as those with no reported SIB. The results of these
analyses suggest that those with persistent and, to a lesser
extent, incident SIB were characterized by lower cognitive
and adaptive behavior scores relative groups with transient
or no SIB. Effects were strongest for measures of receptive
language, gross motor skill, visual reception, and
adaptive and socialization skills. These differences are
consistent with correlational evidence in the SIB literature (e.g.,
Matson et al. 2009) and may inform early intervention
strategies targeted to skill acquisition in specific functional
domains, such as receptive language or social and play
skills, as inoculation against SIB risk.
The present study relied on parent reported repetitive
behavior, aggregating SIB into two categories (i.e., SIB or
no SIB at 24 months based on parent endorsement of any
SIB item on the RBS-R). Direct observation of SIB would
preclude potential biases associated with proxy report
of behavior and could also provide information about the
frequency or function of SIB (e.g., Richman and Lindauer
2005). Further, our analyses relied on reports of occurrence
of SIB without regard to severity. This limitation is related
in part to use of the RBS-R, which is a clinical measure not
necessarily suited to detecting severity among very young
children. Indeed, it is not clear how a parent would judge
severity of self-directed behaviors performed by an infant
or toddler. Future work might address this issue through
more developmentally appropriate or objective means of
quantifying severity, perhaps clarifying the distinction and
developmental relationship between SIB and proto-SIB.
Because the sample evaluated was not restricted to only
incident SIB cases in the logistic regression analyses, we
were unable to directly assess which predictors preceded
the emergence of SIB or proto-SIB. Optimally,
recruitment of a cohort of infants at high risk for ASD that are not
engaging in any SIB at study entry, and prior to the age of
12 months, would facilitate research specific to the
emergence of SIB, while following children to later ages would
provide a clearer understanding as to the natural
progression of SIB and SIB-like behavior. While we did not detect
a significant effect for sex in predicting SIB, this does not
preclude the possibility that such effects were masked by a
disproportionately male sample.
In closing, the purpose of this study was to evaluate
cognitive and behavioral characteristics predicting early SIB
among children at high familial risk for ASD. With only
a handful of studies utilizing a prospective research design
to identify risk factors for SIB during the first years of
life, this study provides an initial examination of risk
factors associated with SIB among young children who are at
elevated risk for ASD. Continued efforts to ameliorate the
deleterious effects and high treatment costs associated with
SIB are warranted, and one promising strategy is to pursue
preventative approaches by identifying early risk factors.
Acknowledgments This work was supported by grants from
the National Institutes of Health under awards K01MH101653,
P30HD03110, and R01HD05574; Autism Speaks, and the Simons
Foundation. We wish to express our gratitude to IBIS families for
continued participation in this research.
Authors’ Contributions AFD drafted the manuscript and
participated in study conception, data analysis and interpretation; KNB,
SRD, AME, JRP, RTS, and LZ participated in acquisition of data and
revising the manuscript critically for intellectual content; JTE
participated in study conception and revising the manuscript critically for
intellectual content; JP participated in study design and conception,
acquisition and interpretation of data, and revising the manuscript
critically for intellectual content; JJW participated in manuscript
preparation, study conception, data analysis and interpretation. All
authors read and approved the final manuscript.
Compliance with Ethical Standards
Ethical Approval All procedures performed in studies involving
human participants were in accordance with the ethical standards of
the institutional and/or national research committee and with the 1964
Helsinki declaration and its later amendments or comparable ethical
Informed Consent Informed consent was obtained from all
individual participants included in the study.
Open Access This article is distributed under the terms of the
Creative Commons Attribution 4.0 International License (http://
creativecommons.org/licenses/by/4.0/), which permits unrestricted
use, distribution, and reproduction in any medium, provided you give
appropriate credit to the original author(s) and the source, provide a
link to the Creative Commons license, and indicate if changes were
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