Research at CAMH

CAMH Connexions

Fall 2006

by Leah Young

SAD and Obesity: What's the Link?

In a recent study, CAMH researchers examined the link between season of birth and body weight in women with Seasonal Affective Disorder (SAD). Led by Dr. Robert Levitan and Dr. James Kennedy, the study examined whether the season a person was born in affected body weight regulation in individuals with sad. Their investigation included possible interaction effects with the 7R allele (specific section of DNA coding) of the dopamine-4 receptor gene that influences weight gain by causing loss of sensitivity to the brain chemical dopamine.

The study revealed that those women born in the spring and carrying the 7R allele (designated the high-risk group) had an average maximum Body Mass Index (BMI) 26% higher than those born in other seasons and without the 7R allele (designated the low-risk group).

These investigators also looked at lifetime rates of obesity and morbid obesity in both the high-risk and low-risk groups. The high-risk group was significantly more likely to experience obesity or morbid obesity: 53% of the high-risk group had obesity at some point in their lives, compared to 20% of the low-risk group. Looking at morbid obesity, 24% of the high-risk group experienced this condition compared to just 4% in the low-risk group.

At a genetic level, these results expand our understanding of weight gain and obesity in women with sad by suggesting that factors linked to birth season, such as early exposure to hormones tied to seasonal light/dark cycles, interact with the dopamine-4 receptor gene to influence body weight regulation in this population.

Overall, these results also point to a novel interaction between a person's genes and the environment during the early stages of brain development, which triggers weight gain and obesity later in life. The authors propose that this phenomenon is the result of a seasonal thrifty phenotype, a historical behavioural strategy programmed in our genes that enhanced survival in northern latitudes. Thousands of years ago, characteristics seen in sad, such as increased eating and decreased activity, were adaptations to, or predictors of, seasonal famine in areas further from the equator. However, in today's environment of plentiful food, these characteristics create an increased risk for obesity in women with sad.

CAMH Research releases new study on Depression Relapse

Major depression is the leading cause of disability worldwide, and more than 50% of people diagnosed experience a relapse in symptoms. Yet little attention is paid to strategies for reducing the risk of relapse, or to measures that identify those people in remission who are at risk for a relapse of depression. CAMH recently released a new study by CAMH's Dr. Zindel Segal that holds promise for the design of more effective treatments that, in addressing this risk, will allow people to get and stay well longer.

The study shows that individuals who have recovered from depression may continue to be at risk for relapse if brief feelings of sadness trigger depressive thinking styles. According to Dr. Segal, "these findings unmask the nature of relapse vulnerability in people who seem well past their problems with depression."

This is the first study to make the link between these differences in thinking styles and the prediction of illness relapse, following successful treatment for depression. The results suggest that treatment approaches directly targeting thinking styles may be an effective tool in preventing depression relapse.

The study revealed that people who achieved clinical remission from depression through antidepressant medication showed greater levels of depressive thinking after a procedure that caused temporary sadness, compared to those who had received cognitive behaviour therapy. Regardless of the type of treatment, the magnitude of depressive thinking that was revealed while patients were briefly sad was a significant predictor of relapse.

The data showed that 51% of participants had a relapse of depression during the follow-up phase of the study. Classifying patients on the basis of how significant the change was in depressive thinking following an experimental induction of sadness allowed for 81% of relapsers to be correctly identified. These results demonstrate a residual but increased risk for relapse that has not been fully addressed by treatment.

In addition to this exciting work, Dr. Segal is studying the effects of a novel treatment that teaches patients how to address these mood-linked changes in thinking styles through the practice of mindfulness meditation. In mindfulness meditation a person practices becoming intentionally aware of his or her thoughts and actions in the present moment, non-judgmentally.

Visit http://archpsyc.ama-assn.org for a full copy of Dr. Segal's paper entitled "Cognitive Reactivity to Sad Mood Provocation and the Prediction of Depressive Relapse."

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