Obsessive-Compulsive Disorder and the Risk of Dementia

Obsessive-compulsive disorder (OCD) is a severe and disabling disorder characterized by intrusive disturbing thoughts (obsessions) and repetitive behaviors to deal with these thoughts (compulsions). Treatments, including medications and psychotherapies, may only partially help to diminish symptoms. This disorder has some characteristics that are typical of anxiety disorders and others that are found in individuals with thought disorders. Symptoms are often chronic.

There is some evidence suggesting that individuals with OCD may be at increased risk for dementia. However, many of the studies to date have been small and used a retrospective design. Recently, Mu-Hong Chen and colleagues published a provocative study in the Journal of Clinical Psychiatry that took advantage of a large insurance database in Taiwan to investigate this question. Their results provide evidence that individuals with OCD may be at higher risk for developing dementias such as Alzheimer’s disease and vascular dementia.

In 1995, a universal single-payer health insurance system was instituted in Taiwan. By 2010, over 99 percent of Taiwanese citizens were enrolled in the program. The Chen group utilized de-identified health information from a research database affiliated with this system to conduct their study.

They identified adults 45 years of age and older who were diagnosed with OCD at least twice by board-certified psychiatrists between January 1, 1996, and December 31, 2013. None had a history of dementia prior to their OCD diagnosis. A matched group of control participants without OCD or dementia was determined on a 1:10 basis, i.e., 10 controls were matched for every person with OCD. The final study included 1,347 individuals with OCD and 13,470 matched controls.

The investigators examined records through December 31, 2013, and recorded diagnoses of dementia in individuals with OCD and matched controls without OCD. Dementia was considered to be present if it was documented at least twice by board-certified psychiatrists or neurologists during the follow-up period. The investigators controlled for potentially confounding variables, including age, sex, other medical conditions, income level, and urbanization (using a scale related to urban versus rural living).

The results were intriguing. During the follow-up period, 1.7 percent of individuals with OCD developed Alzheimer’s disease versus 0.1 percent of controls. About 1.1 percent of those with OCD developed vascular dementia versus 0.2 percent of controls, and 3.6 percent of those with OCD developed unspecified dementia (such as dementia suggestive of Alzheimer’s disease together with co-existing vascular disease) versus 0.5 percent of controls.

After controlling for potentially contributing variables, the chances of a person with OCD developing dementia was more than 4-fold higher than controls.

Men with OCD were more likely to develop Alzheimer’s disease while women with OCD were enriched in the group that developed vascular dementia. This pattern is opposite to what would be expected in a general population.

In those with OCD, dementia was diagnosed about 6 years earlier than in those without OCD (70.5 years of age versus 76.7 years of age). In addition, early-onset dementias, defined as occurring before age 65, were more common in the OCD group (1.7 percent versus 0.1 percent).

If there is an increased risk of developing dementia in those with OCD, why hasn’t this been evident before now? OCD occurs in about 1 to 2 percent of the population. Since it is not overly common, it would be difficult to see a relationship between OCD and dementia by studying all individuals with dementia. An enrichment in the 1 to 2 percent of the population with OCD would be diluted out by the 99 percent without OCD. The study described here examined a large number of persons with OCD and followed them prospectively into older ages to determine how many developed dementia.

Like all findings, these results must be replicated in other longitudinal studies before a clear relationship between OCD and dementia can be established. In the meantime, it appears to make sense for physicians to monitor patients with OCD for signs of dementia.

If these findings are replicated in other studies, elucidating the mechanisms underlying the relationship between OCD and dementia would be a logical next step. In an earlier post, we discussed a study indicating that individuals with schizophrenia may be at increased risk for dementia. Results from both of these studies are consistent with other evidence from longitudinal, prospective studies demonstrating that psychiatric disorders in general, across the range of mental illnesses, are associated with signs of premature aging in middle-aged adults. Unraveling the relationships between various psychiatric disorders, aging, and primary cognitive disorders could lead to a better understanding of the aging process and its relationship to stress and neurologic and psychiatric symptoms. It also remains unclear how psychiatric treatments influence risks of premature aging and cognitive dysfunction, although some evidence suggests that certain psychiatric medications, including those used for OCD, can have beneficial effects.

This column was written by Eugene Rubin M.D., Ph.D., and Charles Zorumski M.D.