Objective: Amphetamine prescribing has increased in the United States in recent years. Previous research identified an increased risk of incident psychosis with prescription amphetamines. The purpose of this study was to examine the impact of dose levels of prescription amphetamines on the risk of this rare but serious adverse outcome.
Methods: A case-control study using electronic health records was conducted to compare the odds of incident psychosis or mania with past-month exposure to prescription amphetamines. Case subjects were patients ages 16-35 hospitalized at McLean Hospital for incident psychosis or mania between 2005 and 2019. Control subjects were patients with an initial psychiatric hospitalization for other reasons, most commonly depression and/or anxiety. Amphetamine doses were converted to dextroamphetamine equivalents and divided into terciles. Secondary analyses evaluated the odds of psychosis or mania with methylphenidate use.
Results: Among 1,374 case subjects and 2,748 control subjects, the odds of psychosis and mania were increased for individuals with past-month prescription amphetamine use compared with no use (adjusted odds ratio=2.68, 95% CI=1.90-3.77). A dose-response relationship was observed; high doses of amphetamines (>30 mg dextroamphetamine equivalents) were associated with 5.28-fold increased odds of psychosis or mania. Past-month methylphenidate use was not associated with increased odds of psychosis or mania compared with no use (adjusted odds ratio=0.91, 95% CI=0.54-1.55).
Conclusions: Although use of hospitalized control subjects excludes individuals with less severe disease, leading to selection bias, the study results suggest that caution should be exercised when prescribing high doses of amphetamines, with regular screening for symptoms of psychosis or mania.
Keywords: Bipolar and Related Disorders; Schizophrenia Spectrum and Other Psychotic Disorders; Stimulants; Substance-Related and Addictive Disorders.