In addition to this mixed evidence, a new philosophy suggests a synergistic relationship between antipsychotic and stimulant medications.2 In patients with schizophrenia, an increase in phasic dopamine (DA) signaling in the mesolimbic pathway is associated with an exacerbation of positive symptoms. Antipsychotic medications act at the postsynaptic DA D2 receptors to block this signaling, causing a reduction in a patient’s positive symptoms. By stimulating presynaptic DA autoreceptors, stimulants also promote a decrease in this signaling, and therefore a reduction in a patient’s positive symptoms. It is important to note, however, that this only occurs at therapeutic doses of stimulant medications. On the other hand, when a stimulant is used at supra-therapeutic doses, an increase in phasic DA signaling occurs, therefore causing an exacerbation of psychosis in a patient. This philosophy suggests that therapeutic doses of stimulants may prove to be beneficial in patients with schizophrenia.

Once a patient has a confirmed diagnosis of ADHD and schizophrenia, it is important to initiate appropriate treatment.2 A suggested treatment algorithm is shown in Figure 1. An important step in the management of these disorders is the treatment of psychosis prior to ADHD. By treating psychosis first, the provider has the ability to determine whether a patient’s ADHD treatment is worsening or improving a patient’s psychotic symptoms. If symptoms persist despite antipsychotic therapy, stimulant and nonstimulant medications as well as nonpharmacological interventions may be used.

Assessing the efficacy of a patient’s treatment is very important so that the next appropriate step in the patient’s management can be decided.2 Efficacy of the treatment can be established by determining the difference in a patient’s symptoms pre- and post- treatment and can be determined by the patient themselves or by a family member. Collaboration with providers and close follow-up and monitoring are also very important aspects for the success of the management of a patient’s ADHD and schizophrenia.

Although understudied, comorbid ADHD and schizophrenia is rather common.1,2 Not only is it difficult to diagnose patients who suffer from both of these disorders, treatment is challenging due to the controversial evidence regarding appropriate therapy. In order to provide the best care for these patients, it is essential to further investigate the available treatment options as well as their benefits and risks for patients with ADHD and schizophrenia. 

References

1.     Huemer J, Sibitz I. Detecting and treating adult attention deficit hyperactivity disorder in a patient with schizophrenia. Neuropsychiatr. 2014 May 20; 28:92-96. DOI: 10.1007/s40211-014-0103-0.

2.     Gough A, Morrison J. Managing the comorbidity of schizophrenia and ADHD. J Psychiatry Neurosci. 2016; 41(5). DOI: 10.1503/jpn.150251.

Figure 1 — Suggested Treatment Algorithm For Comorbid ADHD and Schizophrenia2