A pilot study of the prevalence of psychiatric disorders in PLS and ALS.

The prevalence of psychiatric disorders in primary lateral sclerosis (PLS) is currently unknown. In the present study, we compared the prevalence of psychiatric illness in patients with PLS and amyotrophic lateral sclerosis (ALS). We hypothesized that if the psychosocial stress of motor neuron disease predisposes patients to depressive disorders, patients with ALS (with a poorer prognosis and more disability than patients with PLS) should have a higher prevalence of depressive disorders than patients with PLS. We administered the gold standard of psychiatric assessment, the SCID, to 19 PLS and 13 ALS patients. We found a prevalence of current depressive disorders in PLS patients that was, by a non-significant trend, lower than that of ALS patients. The prevalence of current depressive disorders in the ALS patients was higher than previously reported and similar to that observed in non-neurological medical disorders. Other psychiatric disorders were rare. In conclusion, depressive disorders were the most commonly observed psychiatric disorders in both PLS and ALS. By a non-significant trend, the PLS patients had a lower current prevalence of depressive disorders than the ALS patients. These data are consistent with the hypothesis that the psychosocial stress of MND is a risk factor for depression.