A Mayo Clinic study has shown that the onset of REM Sleep Behavior Disorder (RBD) at a younger age appears to be connected to antidepressant use.

RBD is a sleep disorder where patients act out their dreams, which are often unpleasant and violent, according to Maja Tippmann-Peikert, M.D., sleep medicine specialist, neurologist and study investigator. This acting out results from a loss of normal muscle paralysis in REM (rapid eye movement) sleep, the dream stage of sleep, which normally prevents enacting one’s dreams. RBD patients generally act out their dreams in a defensive posture, as if fending off an attacker, says R. Robert Auger, M.D., Mayo Clinic sleep medicine specialist, psychiatrist and primary investigator. The disorder is often recognized by a bed partner.

Although previously published case reports and a more recently published study have suggested the association between antidepressants and RBD, this study represents the first systematic demonstration of the relationship. Findings will be presented June 19 at the Associated Professional Sleep Societies’ SLEEP 2006 meeting in Salt Lake City.

“Our findings suggest that RBD in younger patients - in the 30s instead of the usual age of the 50s or older - is frequently linked to antidepressant use,” says Dr. Auger. “I’d interpret this to mean one of three things: 1) in younger patients, antidepressants can cause RBD, or 2) in younger patients, RBD results in psychiatric diagnoses that then result in antidepressant prescriptions, or 3) a common factor is causing both the RBD and the psychiatric diagnoses, which in turn results in antidepressant prescriptions. If medications are implicated in a direct manner, it may be an idiosyncratic effect, it could be related to the dose of medication, or the medications simply may be unmasking an underlying predisposition to RBD.”

To conduct this study, investigators reviewed records of patients consecutively diagnosed with RBD at Mayo Clinic between 2002 and 2005, removing those with neurodegenerative diseases such as Parkinson’s disease or dementia at the time of RBD diagnosis. Twenty patients diagnosed when they were less than 50 years old (average age 34) were age- and gender-matched for comparison to a group of patients without RBD.

Equivalent comparisons were performed in patients diagnosed with RBD over age 50. After looking at all groups, the investigators found that the younger RBD patients were unique with respect to greater use of antidepressants than those without RBD (80 percent versus 15 percent use). Antidepressants prescribed for these patients spanned all types: selective serotonin reuptake inhibitors (SSRIs), venlafaxine, mirtazapine and tricyclic antidepressants. The investigators also found a higher prevalence of females in the early-onset group of RBD (45 percent female) patients than in older-onset RBD (13 percent female). RBD is known to be largely a male disease.

A link between antidepressants and RBD is not completely surprising, according to Dr. Auger, as the neurotransmitters affected by these medications are involved in REM sleep regulation, and a recent study shows that they diminish the muscle paralysis associated with normal REM sleep.

Dr. Auger says that due to the retrospective nature of the study, correlation but not direct causality between antidepressants and RBD can be inferred.

“From the results of our study, it appears that young-onset RBD is frequently associated with antidepressants,” says Dr. Auger. “It nevertheless appears to be a relatively rare phenomenon, so I don’t think one should hesitate to take an antidepressant based on this particular risk. Physicians should be aware of this potential side effect, however, particularly in patients who complain of sleep disturbances. I’m hoping these findings will create a greater awareness, as practitioners generally would not link medications with RBD.”

There are no treatments available for those prescribed antidepressants to prevent them from later developing RBD, but the condition is generally quite treatable once identified, he says. It is uncertain whether this younger group of patients possesses the same risk of developing a neurodegenerative disease later in life, as has been described in previous studies involving patients with older-onset RBD.

Currently, 10 million Americans take antidepressants.