The risk of severe depression, psychosis or panic attacks with prophylactic antimalarials

Experimental and observational studies have linked mefloquine use to an increased risk of developing neuropsychiatric adverse effects such as depression or psychoses. Most of these reports relied on interview-based information from travellers. We conducted a population-based observational study using a database of medical records to quantify and compare the risk of psychiatric disorders during or after use of mefloquine with the risk during use of proguanil and/or chloroquine, or doxycycline.

The study population was drawn from the large UK-based General Practice Research Database (GPRD). Subjects were aged from 17-79 years and were exposed to mefloquine, proguanil, chloroquine or doxycycline (or a combination of these drugs) at some time between 1990 and 1999. We performed a person-time and a nested case-control analysis to assess the risk of developing a first-time diagnosis of depression, psychosis or panic attack during or after use of these antimalarial drugs.

Within the study population of 35 370 subjects (45.2% males), we identified 580 subjects with a first-time diagnosis of depression (n = 505), psychosis (n = 16) or panic attack (n = 57) and two subjects committed suicide. The incidence rates of first-time diagnoses of depression during current use of mefloquine, proguanil and/or chloroquine, or doxycycline, adjusted for age, gender and calendar year, were 6.9 (95% CI 4.5-10.6), 7.6 (95% CI 5.5-10.5) and 9.5 (95% CI 3.7-24.1)/1000 person-years, respectively. The incidence rates of psychosis or panic attacks during current mefloquine exposure were 1.0/1000 person-years (95% CI 0.3-2.9) and 3.0/1000 person-years (95% CI 1.6-5.7), respectively, approximately 2-fold higher (statistically nonsignificant) than during current use of proguanil and/or chloroquine, or doxycycline. The nested case-control analysis encompassed 505 cases with depression and 3026 controls, 16 cases with psychosis and 96 controls, and 57 cases with a panic attack and 342 controls. Current use of mefloquine was not associated with an elevated risk of developing depression. In a comparison between patients currently using mefloquine with all past users of antimalarials combined, the risk estimate was elevated for current users of mefloquine for both psychosis (odds ratio [OR] 8.0, 95% CI 1.0-62.7; p < 0.05) and panic attacks (OR 2.7, 95% CI 1.1-6.5; p < 0.05).

The absolute risk of developing psychosis or panic attack appears low with all the antimalarials tested. No evidence was found in this large observational study that mefloquine use increased the risk of first-time diagnosis of depression when compared with the use of other antimalarials investigated in this study.