Comorbidity across childhood-onset neuropsychiatric disorders

Background: Attention-Deficit/Hyperactivity Disorder (ADHD), and Autism Spectrum Disorders (ASDs) are clinically found to be comorbid with each other and with other psychiatric conditions to a greater extent than what is previously assumed. It is, however, difficult to capture this complexity using current diagnostic systems, where exclusion criteria prevent simultaneous diagnosis. Thus, in order to describe this complexity and its consequences for the individual, it is important to describe actual comorbidity in different clinical contexts. Aims: The overall purpose of this thesis was to describe the prevalence and comorbidity between ASD and ADHD, and other psychiatric conditions. Specific aims were to: describe comorbidity in a group of adult out-patients with ADHD and/or ASDs (Paper I); investigate the prevalence of personality disorders and describe the personality profiles of the same group (Paper II); describe psychiatric symptoms associated with aggressive behaviors in adult psychiatric patients (Paper III); describe comorbidity in a group of adolescents placed in special youth institutions (Paper IV); and to investigate whether comorbid ADHD and substance abuse is associated with a more negative outcome, that is, more criminal recidivism, health care needs, and untimely death (Paper V). Methods and results: Paper I-II are based on diagnostic and demographic cross-sectional data showing that ADHD and ASD overlap greatly with each other, and that there is a significant overlap between ADHD and bipolar disorder and ASDs and psychosis. Personality disorder diagnoses are also common in these diagnostic groups, showing specific personality profiles associated with ADHD, ASD, and those with comorbid ADHD and ASD. In Paper III aggressive behaviors in a group of policlinic psychiatric patients have been compared with a group of forensic psychiatric patients, and both groups reported similar high levels of aggressive scores. Paper IV is based on cross-sectional data on institutionalized adolescents, which in Paper V has been combined with longitudinal follow-up data. Psychiatric diagnoses in general, and specifically the occurrence of ADHD and ASD, is high. Criminal recidivism and health care use was overall very high, while there were small differences between the groups with comorbid ADHD and SUD, SUD only, and, finally, no SUD in respect to criminal recidivism, health care needs and untimely death. Conclusion: Comorbidity between ADHD and ASD and other psychiatric diagnoses are common among psychiatric patients, and in many cases associated with character immaturity, aggression and personality disorders. It also seems as the outcome over time tends to worsening with increasing comorbidity, especially in cases with comorbid substance abuse and neuropsychiatric disorders. These complex states constitute diagnostic and treatment challenges for psychiatry and its classic divisions between child and adolescent versus adult psychiatry, mental illness versus personality disorders, and psychological versus medical interventions