Autism spectrum disorders and psychiatric comorbidities: a narrative review

Background. Autism spectrum disorders (ASD) are a group of neurodevelopmental disorders characterized by persistent difficulties in social communication, restricted interests, and repetitive behaviors. Diagnosis can be difficult because of the heterogeneity of clinical and subclinical expression of symptoms among individuals. ASD rarely presents in its pure form, and individuals with ASD are more likely to have comorbid psychiatric disorders than the general population. Symptoms related to psychiatric comorbidities can worsen the clinical course of ASD, and distinguishing psychopathological symptoms from the main or atypical symptoms of ASD can be difficult for clinicians. The aim of this narrative review is to make an overview of psychiatric comorbidities of ASD, updating prevalence, highlighting symptoms and available diagnostic tools, and finally defining possible treatment strategies. Methods. This narrative review was conducted first by defining the objective, followed by a research of the scientific literature and data evaluation, and finally by presenting results. Search terms were entered into ERIC, MEDLINE, PsycARTICLES, PsycINFO, Scopus, and PubMed. Only studies published in English were included. Only studies that analyzed autistic traits in severe mental disorders and studies of patients with ASD and severe mental disorders in comorbidity were included. Studies on children, adolescents, and adults were included. Given the breadth and specificity of the topic, studies on psychosis, schizophrenia, gender dysphoria, trauma and post-traumatic stress disorder, substance use disorders, and suicidal behavior were not included in the search terms and are not discussed in this review. The terms and databases were combined using the Boolean search technique to make the search more restrictive and detailed. Tables were then constructed and results were sorted by prevalence, symptoms, diagnostic tools and treatment, and finally discussed in a narrative way. Results. The included studies were divided into eight categories based on psychiatric comorbidity in ASD: attention deficit hyperactivity disorders; anxiety disorders; personality disorder; repetitive behaviors and obsessive compulsive disorders; sleep disorders; mood disorders; Tourette syndrome and tic disorder studies; feeding and eating disorder studies. Discussion. ADHD has the highest prevalence among psychiatric comorbidities in ASDs, followed by anxiety disorders. The clinical presentation of all the disorders considered is often overlapping with core symptomatology of ASD, although some peculiarities may help clinicians to recognize the presence of a comorbidity. With the exception of few scales adapted for ASD patients, assessment tools available for the diagnosis of psychiatric disorders in the context of ASD are often not adjusted for individuals on the autism spectrum. The co-occurrence of these disorders is usually associated to a worsening of the clinical presentation and to a resistance to conventional treatments, especially pharmacological. Among non-pharmacological treatments, behavioral interventions, and specifically cognitive behavioral therapy, seem to be effective in almost all the psychiatric disorders evaluated in this study. Conclusions. Prospective studies with homogeneous samples are needed to develop specific diagnostic tools and dedicated treatments for psychiatric comorbidities in the context of ASD.