Past reports have suggested that antiphospholipid (aPL) antibodies may emerge as a response to antipsychotics treatment, as a high prevalence of aPL antibodies in antipsychotics users has been observed. However, no control group of non-medicated psychiatric patients was included in these reports. In a cross sectional study we determined the prevalence of aPL antibodies in 333 psychiatric inpatients. We compared the proportions of positive aPL antibodytests between users and non-users of antipsychotics with adjustments for potential confounders. The proportion of antipsychotics users carrying at least one aPL antibody ranged from 10*8% to 27*0% compared with 6*8% to 27*2% in non-users (P = 0*24, P = 0*24) depending on the method of detection of lupus anticoagulant (LA). The prevalence of LA detected by dilute Russell viper venom time or partial thromboplastin time-LA was not different between antipsychotics users and non-users (8*1% vs. 5*4%, P = 0*53 and 18*4% vs. 18*2%, P = 0*22), as well as the prevalence of IgM and IgG anti-β2-glycoprotein-I antibodies, IgM and IgG anti-cardiolipin antibodies(3*8% vs. 2*0%, P = 0*75, 0*0% vs. 0*0%, P = not applicable, 1*1 vs. 1*4%, P = 0*91, 2*7% vs. 3*4%, P = 0*71). In conclusion, aPL antibodies were frequently found in patients with psychiatric diseases and no significant increase in the prevalence of aPL antibodies was observed in antipsychotics users.