The Relation Between Autism Symptom Severity and Family History of Psychiatric and Neurodevelopmental Disorders

Background:  It is known that Autism Spectrum Disorder (ASD) is associated with family history of psychiatric disorders in addition to rates of autism and other neurodevelopmental disorders.  Studies disagree about which psychiatric disorders are most prevalent in families of those with ASD, although epidemiological studies support a link between autism and familial mood and anxiety disorders (Smalley, McCracken, & Tanguay, 1995).  Research indicates relationships between positive family history and higher IQ or increased functional ability (Mazefsky, Williams, Minshew, 2008; Robinson, et. al 2014).  Studieshave yet to examine how family psychiatric history may correlate to measures of autism severity.

Objectives:  To investigate whether the presence of psychiatric and neurodevelopmental disorder history in first- and second-degree relatives in a population of children and adolescents diagnosed with ASD is related to autism severity in the proband.

Methods:  Participants were children and adolescents with ASD (n = 338, 3-17 years old) selected from a state-wide autism patient registry (80.5% male, mean age 9.9 years).  ASD diagnoses were confirmed by the Autism Diagnostic Observation Schedule (ADOS).  Family history of psychiatric and neurodevelopmental disorders was obtained through parental interviews.  The presence of psychiatric and neurodevelopmental disorders in first- and second-degree relatives was summed to create four composite variables (i.e, sum of psychiatric disorders and neurodevelopmental disorders in 1^st and 2^nd degree relatives).  The psychiatric family history composite consisted of fifteen disorders (e.g., mood and anxiety disorders), and the neurodevelopmental disorder composite consisted of eight disorders (e.g., ASD, Learning Disabilities, Intellectual Disability).  Estimates of proband symptom severity were based on the caregiver-completed Social Responsiveness Scales, 2^ndEd. (SRS-2) total T scores and the ADOS standardized severity score.  Gender-controlled linear regression was used to investigate the relationship between family history of psychiatric and neurodevelopmental disorders and autism severity scores. 

Results:  First-degree family history of psychiatric disorders was related to increased symptom severity on the SRS-2 measure (beta = .159, p = 0.009).  There was no significant relation between first- or second-degree family history of neurodevelopmental disorders and SRS-2 severity measure, nor a significant relation between family history of neurodevelopmental disorders or psychiatric disorders and ADOS symptom severity.  Follow up analyses of psychiatric disorders revealed that first-degree family history of depression was significantly associated with higher SRS-2 scores, even after statistical correction (t(290) = -3.31, p= .001), while no other disorders showed a statistically significant trend.

Conclusions:  The increase in presence of family history of psychiatric disorders in first-degree relatives was related to an increase in severity of social deficits in the autism spectrum measured by the SRS-2.  These findings implicate a positive psychiatric family history as a higher genetic liability toward autism severity, but we also must consider the possibility that an increase in more “problematic” behaviors in children may contribute to a reporting bias in parental psychiatric disorders such as depression or anxiety.  Our results support existing research that stresses the importance of investigating psychiatric family history as a potential contributing factor to behavioral ASD phenotypes.