Comorbid psychiatric disorders

Psychiatric disorders can be under- or over-diagnosed when they are comorbid with autism spectrum disorder; see Principles of assessment of psychiatric disorders in people with developmental disability. Where possible, consult with clinicians who are experienced in the diagnosis and management of autism spectrum disorder. The following psychiatric disorders are more common in autism spectrum disorder:

• anxiety disorders—extremely common in autism spectrum disorder, can severely affect functioning; may be exacerbated by sensory sensitivities, intolerance of change and difficulties in expressing emotion
• depression
• bipolar disorder—more likely to present with irritability than grandiosity in developmental disability
• psychosis, schizophrenia—significantly more common in autism spectrum disorder than the general population; it is important to understand the person’s baseline measure of functioning and to assess their current level of functioning. Functional impairment in the presence of possible psychotic symptoms requires assessment and treatment
• obsessive compulsive disorder (OCD)—consider diagnostic criteria as OCD can be mistaken for the core features of autism spectrum disorder (ie restricted interests, intolerance of change)
• suicide—significantly increased risk; inability to communicate emotion can mask severity of suicidality. Suicidal and homicidal thoughts must be expressly asked about and taken seriously, even if the person does not seem distressed (see Self-harm and suicide risk)
• eating disorders—more common in autism spectrum disorder and can be severe, requiring specialist management
• gender dysphoria—autism spectrum disorder can be associated with a pervasive feeling of being different, confusion about identity, and a feeling of not belonging. If gender dysphoria is present, refer for specialist assessment by a psychiatrist or specialised gender clinic
• catatonia—can complicate mental or physical illness, but also commonly occurs as an isolated comorbidity in autism spectrum disorder; can deteriorate to affect oral intake and result in severe decline in function.