Prevalence of depression is higher in women than men. Among women, the prevalence is higher among those who are divorced (26. 5 per cent) and widowed (20 per cent) compared with those who are married (15 per cent)

A study of more than 25,000 individuals above the age of 20 (median age 40) in Chennai found nearly 15 per cent of them had depression. The results are published online today (September 28) in the Open Access journal PLoS One.

The study conducted by Dr. V. Mohan and others from the Madras Diabetes Research Foundation, Chennai, found that depression was more prevalent in females (15.1 per cent) compared with males (13.9 per cent).

“We studied the general population, and the results are a true representation of Chennai,” said Dr. V. Mohan, Chairman of Dr. Mohan’s Diabetes Specialities Centre, Chennai. “Other Indian studies were restricted to only certain populations, and were not a true representation of the general population of both sexes. The number of subjects studied was also less [than 400].”

The study was based on 12 parameters that were validated and published in February this year in the Journal of Association of Physicians of India. “A person is said to suffer from depression only if he or she answers 'yes' to at least 5 questions,” said Dr. Mohan. “And the individual is asked to quantify the period if his answer is 'yes', say inability to fall asleep.”

The study found that nearly 31 per cent of the people studied suffered from depressed mood. This was closely followed by tiredness (30 per cent). Severe symptoms of depression such as suicidal thoughts (12 per cent) were less common.

The study brought out several other associations. Depression was found to be inversely related to income and education. In other words, prevalence of depression was higher among people who had less income and education.

Among women, prevalence was higher among those who were divorced (26. 5 per cent) and widowed (20 per cent) compared with those who were married (15 per cent). Many studies undertaken in developed countries have shown similar associations.

Age appeared to play a significant role. It found that the chances of getting depressed increased as individuals grew older. Again, women were found to be more susceptible to depression as they grew older.

“Age, marital status, education, income, etc., are only associations and not causal factors,” said Dr. Mohan.

Unlike what was seen in studies conducted in the U.S., depression did not appear to dip in the middle age of 45 and then start rising again but kept increasing steadily with age.

The higher association between suicidal tendencies and depression (about 12 per cent) was based on individual’s response to a question of “thoughts about death” than suicidal thoughts in particular.

The high prevalence, according to the authors, could be because unlike other studies that looked at suicidal plans or ideation, the questionnaire used in this study was restricted to “thoughts about deaths in general.”

“We could only ask thoughts about deaths in general and not about the individual’s suicidal tendencies,” Dr. Mohan said.

The study did not look into any confounding effects that could alter the results.

People chosen for this study were recruited from the urban component of the Chennai Urban Rural Epidemiological Study (CURES).

“This is the largest study undertaken in India to know the prevalence of depression in the general population and looked at all strata in the city,” said S. Poongothai from the same Centre, and the first author of the study.

People chosen for this study were from ten zones representing 46 wards in Chennai. The subjects were selected following a set procedure that minimised any selection bias.

The 12 parameters used to study depression

The conclusions of the study were based on a questionnaire, where individuals were required to either state 'yes' or 'no' to a set of 12 questions. To reflect Indian conditions, the internationally used questionnaire was improvised and it contained 12 questions instead of nine.

The 12 parameters used were: Feeling sad, blue or depressed; loss of interest or pleasure in most things; feeling tired or low on energy most of the time; loss of appetite or weight loss; overeating or weight gain; trouble falling asleep or staying asleep; sleeping too much; more trouble than usual concentrating on things; feeling down on yourself, no good or worthless; being fidgety or restless; moved or spoke so slowly that other people could notice; thoughts about death more than usual, either your own, someone else’s, or death in general.