Health Scan: Repetitive behavior and depression

ritualistic behavior develops as a way to induce calm and manage stress; Depression can lead to increased risk of stroke.

October 9, 2011 03:21
Feeling sad when you're supposed to feel happy.

311_depression. (photo credit: MCT)

Humans are not the only ones to show repetitive behavior – animals do too.
Provided it isn’t exaggerated (as manifested by obsessive-compulsive disorder, or OCD), it can minimize stress, according to a researcher at Tel Aviv University.

Prof. David Eilam and his graduate student Hila Keren of TAUs zoology department at the George S. Wise Faculty of Life Sciences found that both humans and animals normally exhibit repetitive behavior in general – and especially ritualistic-like behavior. They concluded that ritualistic behavior in both humans and animals developed as a way to induce calm and manage stress caused by unpredictability and uncontrollability, heightening our belief that we are in control of a situation that is otherwise out of our hands. Carried out in collaboration with Prof. Pascal Boyer of Washington University and Dr. Joel Mort of the US Air Force Research Laboratory, the research was recently published in Neuroscience and Biobehavioral Reviews.

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Eilam explains that almost every human and animal activity can be divided into three parts – preparatory, functional and confirmatory. The functional aspect is defined by the specific actions that must occur in order to complete a task. But the preparatory and confirmatory actions, dubbed “head” and “tail” actions by the researchers, are not strictly required to get the job done. We complete them both before and after the central task, but they are not necessarily related to it. Individuals complete different head and tail activities for every task.

During their study, Eilam and his colleagues watched and analyzed videotapes of people completing common tasks such as putting on a shirt, locking a car, or making coffee, as well as basketball players completing a free-throw. In the case of basketball players, explains Eilam, all they actually need to do to complete their action is throw the ball. So why, he asked, is there ritualistic behavior preceding the throw such as bouncing the ball exactly six times? “The routine they perform in the moments before shooting the ball is a method to focus their full concentration and control their actions,” he says. “It’s also an essential part of sports psychology. If players feel that completing their repetitive actions will enhance their performance, they tend to be more successful. This could include anything from locker room antics to LeBron James’s infamous pre-game chalk toss.”

Even in the context of daily activities, head and tail activities can be differentiated quite easily from the functional action in between – but they are exaggerated in OCD sufferers, who might, for example, check and recheck whether the stove has been turned off. These idiosyncrasies are like fingerprints, says Eilam, unique to each individual.

While everyone exhibits repetitive behavior, not everyone’s behavior is obsessive, the researchers say. OCD patients present a pathological tendency towards repetitive behavior or thought patterns. OCD patients were observed to engage in more tail activity than basketball players, who displayed more “head” activity, says Eilam. Those with OCD suffer more than the basketball players from a feeling of incompleteness – they are unsure whether or not their task has been completed, and compulsive behavior is driven by a need to verify the action. Unlike a free-throw, where there is a distinct cue – throwing the ball – which that signals the end of the action, a common compulsive behavior such as washing one’s hands might not have as clear an ending. There is no external reference to indicate “absolutely clean.”

Because those who suffer from OCD can set themselves complicated routines, they often cannot trust that they have fully completed an action, thereby extending the confirmatory tail phase of an action. This is the key difference between normal and pathological rituals, Eilam concludes.


Depression can lead not only to self harm and suicide, but also to increased risk of suffering a disabling or fatal stroke, according to a meta-analysis of 30 studies encompassing some 300,000 patients.

“Stroke is a leading cause of death and permanent disability, with significant economic losses due to functional impairments,” says Dr. An Pan of the Harvard School of Public Health in Boston. “Depression is highly prevalent in the general population, and it is estimated that 5.8 percent of men and 9.5% of women will experience a depressive episode in a 12-month period.

The lifetime incidence of depression has been estimated at more than 16% in the general population. Whether depression increases the risk of stroke has been unclear.”

Dr. Pan led a systematic review and metaanalysis of prospective cohort studies to describe the association between depression and risk of total and subtypes of stroke.

The researchers found that when the data from the studies were pooled, analysis indicated that depression was associated with a 45% increased risk for total stroke; a 55% increased risk for fatal stroke; and a 25% higher risk for ischemic stroke (caused by a blood clot in the brain); but was not associated with an increased risk of stroke due to brain hemorrhage.

The researchers speculate that depression may contribute to stroke through a variety of mechanisms, including known nervous system and endocrine system and immunological/ inflammation effects; poor health behaviors such as smoking, physical inactivity, poor diet, not taking prescribed medicines and obesity; having other major disorders such as diabetes and hypertension and antidepressant medication use.

“In conclusion, this meta-analysis provides strong evidence that depression is a significant risk factor for stroke. Given the high prevalence and incidence of depression and stroke in the general population, the observed association between depression and stroke has clinical and public health importance. More studies are needed to explore the underlying mechanisms and elucidate the causal pathways that link depression and stroke,” the researchers said.

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