Attention deficit hyperactivity disorder: transition to psychotic disorders

It is well recognized that Attention-deficit/hyperactivity disorder (ADHD) is associated with heightened risk for common psychiatric disorders; early identification and treatment of ADHD may help reduce some of this risk. However, the substantially increased risk of bipolar disorder, psychosis, and schizophrenia (hereafter psychotic disorders) is often overlooked (odds ratios 4.7-8.9). Given how common ADHD is, there is growing pressure for greater involvement of primary care services, especially for less complex forms of ADHD. However, those at highest risk for transition to a psychotic disorder need to be prioritised for secondary care follow up. Currently it is unknown how to stratify ADHD according to risk or indeed why only some develop a psychotic disorder. This perspective examines key hypotheses that may explain why transition occurs only in a subset of individuals. One hypothesis is that features suggestive of ADHD may represent early manifestations of psychotic disorders, although direct support for this is limited. The potential role of ADHD treatment is also considered; current data indicate that therapeutic use of methylphenidate is not associated with increased risk of psychotic disorders, while uncertainty remains for amphetamines. The possible mediating roles of ADHD-evoked environmental exposures are discussed, but evidence for mediation is lacking. We also consider the evidence that ADHD and psychotic disorders result from shared underlying neurodevelopmental processes. We highlight key clinical implications for screening and monitoring individuals with ADHD for psychotic disorders and consider what factors may help in weighting risk. Finally, we identify important evidence gaps for future research.