First Glance

Depression is a normal emotion. In certain situations and circumstances it becomes either unbearable or problematic. Depression is ubiquitous. All people at some time or the other experience low mood, low spirits, disinterest or disgust. The word depression has been interchangeably used to describe a symptom, a syndrome, and a disease in the classic meanings of those words. Because of the very diversity of depression in all its aspects, the problems at both theoretical and clinical levels are at once stimulating, challenging, and often frustrating.

Epidemiology of depression

How common is depression?

Depressive disorders are one of the commonest types of psychiatric disorders. The commonest psychiatric problem the general practitioner or family physician is likely to encounter is depression, in some form or the other. It is also the commonest disorder which is likely to be missed, go undetected or inappropriately treated. A major psychotic episode, let us say, of schizophrenia, can be diagnosed and treated with much more ease than an episode of mild or moderate depression.

Epidemiological data on depression in India has been gathered from two sources the general population and clinics. Clinic-based studies have noted rates of 6% to 35%. Thus, depression seems to be a common disorder. However, there is a marked variability in the rates of neurotic or reactive depression compared to manic depressive psychosis (MDP). This could be because persons with depressive symptoms independent of diagnosis constitute heterogeneous groups and are difficult to interpret epidemiologically.

Gender differences

Depression is consistently found to be more common in women than in men at a ratio of approximately 2 to 1. While morbidity is higher in women, mortality in the form of suicide is greater in men. Suicidal attempts (parasuicide) on the other hand are more common among women.

Age variations

Although there are indications that the incidence of depression is highest at middle age, it occurs at all ages. There are certain characteristics of depression which are peculiar to the two ends of the age spectrum, childhood and the elderly.

Other demographic variations

There are indications of higher rates of depression in North India compared to South India. The exact reasons are unknown, and this difference may be an artefact. Common reasons for this variability are thought to include diagnostic practice and bias/tolerance to depressive symptoms, genuine differences in susceptibility to illness as well as in its frequency of occurrence or demographic and cultural differences.

What are the risk factors?

A number of risk factors associated with affective disorders have been noticed: a higher prevalence in females, persons engaged in business, certain castes and males living in joint families has been noted. The common vulnerable age group seems to be 35 years to 54 years in males and 15 to 34 years in females. Depression is noted to be commoner in female patients coming from a lower socioeconomic background.

What causes depression?

No single factor can possibly explain the complex human experience of depression. Thus, depression is considered to be a multifactorial disorder. The contribution of each of the factors may be different in each case. The various factors identified to be involved in the causation of depression are discussed in the following paragraphs.

Genetic factors

It is clear that hereditary factors predispose some individuals to the development of depression. In this connection, it is not the occurrence of depressive disorders in the family members of the individuals but also a number of other illnesses, considered as depressive spectrum disorders, could be involved. The occurrence of these depressive spectrum disorders like alcoholism, drug abuse, suicide, or antisocial personality also predispose the individual to develop depression. Similarly, occurrence of somatisation and chronic pain in the family members is considered as predisposing the individual to develop depression.

Environmental factors

These are very easily acknowledged in most cases. Environmental factors are considered to be etiologically important in some types of depression. These may occur in the form of either changes in the internal environment, for example intercurrent or chronic illnesses or medications which can cause depression or the more frequently identified external environments in the form of different stresses. External environmental factors can be demonstrated in many types of depression but are certainly not involved in the causation of every depression.

Life events

Life events are important changes occurring in the individual's life which produce stress and require adaptability from the individual. Positive and negative social experiences and relationships seem to play an important role in the development of some but not all forms of depression.

Other factors

The final expression of many etiologic factors of any depression is the biological reaction of the individual, which is certainly manifested in biochemical changes and psychological and behavioral ones also.

For clinical purposes, a detailed study of all theoretical factors involved in depression is less important than careful observation and timely intervention for the depressed patients. Thus, a thorough evaluation of the depressed patient should include assessing family morbidity, environmental, social and physiological factors to understand the contribution of each factor to the development of depression in the individual.