Supplementary Material for: Clozapine-Associated Obsessive-Compulsive Symptoms and Their Management: A Systematic Review and Analysis of 107 Reported Cases

<b><i>Background:</i></b> It is not uncommon to find obsessive-compulsive symptoms (OCS) in patients treated with clozapine. These symptoms are attributed to anti-serotonergic effects of clozapine. The objective of this study was to conduct a systematic review of reported cases of clozapine-associated OCS to better understand the nature and management of these symptoms. <b><i>Methods:</i></b> MEDLINE, Embase, and PsycINFO databases were searched with no publication year or language restrictions. Studies reporting cases of clozapine-associated OCS, either de novo or exacerbation of preexisting OCS, were included. The final search date was July 11, 2019. <b><i>Results:</i></b> Fifty-seven studies, involving 107 cases (75 de novo, 32 exacerbated OCS), were included. Clozapine triggered moderate-severe OCS at varying doses (100–900 mg/day) and treatment durations (median 6 months, interquartile range 2–24 months). Higher severity was significantly associated with preexisting OCS, poorer insight into OCS, and active psychosis at the time of OCS. Common strategies to treat clozapine-associated OCS included adding selective serotonin reuptake inhibitors, clomipramine, or aripiprazole, often accompanied by clozapine dose reduction. The rate of response to antidepressants was 49% (29/59), where younger age, shorter duration of underlying illness, shorter cloza­pine treatment duration, better insight into OCS, and presence of taboo thoughts were significantly associated with antidepressant response. Subsequent clozapine dose reduction was effective in many non-responders, where aripiprazole was simultaneously added in 50% (8/16). <b><i>Conclusions:</i></b> Clozapine can trigger severe OCS. Adding aripiprazole with/without clozapine dose reduction may be a good alternative to antidepressants for managing clozapine-associated OCS. Clinicians should be more vigilant about these adverse effects and administer appropriate treatments.