To identify the exposure factors associated with the length of stay of psychiatric patients. A case-control study was performed at a psychiatric hospital in Brazil. The cases included all hospitalised patients with stays of over 60 continuous days over a 1-year period. The randomly chosen controls were matched by gender and age. Multivariate analyses using logistic regression were performed. A total of sixteen patients were selected. There were 72 cases (5.5% of all hospitalisations) and 144 controls; 63.9% were male, and the mean age was 44.4 years (± 11.9). The reasons for hospitalisation were risk to self and the inability to provide for self-care coupled with inadequate family/social support that were shown to be associated (p < 0.05) with length of stay of these psychiatric patients. Additional analytical studies to investigate the quality of life of long-term psychiatric hospitalisation patients are recommended.