Insomnia and nocturnal movement disorders

Little is known about the prevalence of nocturnal movement disorders in patients with insomnia or psychiatric disorders. However, it is well established that sleep-related motor disorders (movement disorders, parasomnias) are associated with psychopharmacological treatment. In a recent prospective study it has been shown that second-generation antidepressants may induce or worsen symptoms of restless legs syndrome (RLS) which is often associated with insomnia. While pure SSRIs and SNRIs carried an average risk of about 5% for triggering RLS, reboxetine did not seem to induce this syndrome. By contrast, mirtazapine caused or worsened RLS in almost 30% of the patients surveyed (Rottach et al., 2009). Other studies using polysomnography have reported an increased risk of periodic leg movement disorder with antidepressant treatment. It was reported that SSRIs and venlafaxine, but not bupropion, increased the risk of periodic leg movements during sleep (PLMS), suggesting that PLM activity seen in association with antidepressant administration might be serotonergically mediated (Yang et al., 2004). Sleep-related movement disorders may also occur under treatment with first- or second-generation neuroleptics (Cohrs et al., 2008). Administration of antidepressants may also induce the occurence of rapid eye movment (REM) sleep parasomnias such as REM sleep behaviour disorder (RBD) (Thomas et al., 2007). Own preliminary data of an ongoing study revealed that sleep-disordered patients with comorbid psychiatric disorders are more likely to report a variety of nocturnal movement disorders using the Munich Parasomnia Screening Questionnaire. However, whether this result is due to the psychopharmacological medication remains to be determined.