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Depression is characterized by depressed or sad mood, diminished interest in activities which used to be pleasurable, weight gain or loss, psychomotor agitation or retardation, fatigue, inappropriate guilt, difficulties concentrating, as well as recurrent thoughts of death. But depression is more than a “bad day”; diagnostic criteria established by the American Psychiatric Association dictate that five or more of the above symptoms must be present for a continuous period of at least two weeks.1 As an illness, depression falls within the spectrum of affective disorders.

Depression poses a substantial burden globally – and to the individual suffering from this disorder. As research has found that interpersonal relationships are particularly likely to suffer when someone is depressed, data suggest that few families or networks of friends are likely to remain unaffected by depression.

The urgency of the rate of depression to public health is likely compounded by the recognition that – if not effectively treated – depression is likely to lapse into a chronic disease. Just experiencing one episode of depression places the individual at a 50% risk for experiencing another, with subsequent episodes raising the likelihood of experiencing more episodes in the future.2

Major depression frequently goes unrecognized and untreated and may foster tragic consequences, such as suicide and impaired interpersonal relationships at work and at home. The use of medications and/or specific psychotherapeutic techniques has proven very effective in the treatment of major depression, but this disorder is still misconstrued as a sign of weakness, rather than being recognized as an illness.

Dysthymia, a depressive disorder characterized by low-grade mood impairment of at least two years, and, commonly, with an initial presentation in childhood or young adulthood.3 Dysthymia has been likened to a less severe major depression, but one more likely to assume a chronic course. Current thinking holds that aggressive treatment of dysthymia is warranted, as many suffering from this disorder develop major depression or may experience the two disorders concurrently.

Depression as a Correlate of Adverse Health Behaviors

In addition to being a chronic disease in its own right, the burden of depression is further increased as depression appears to be associated with behaviors linked to other chronic diseases. In most studies, it is difficult to determine whether depression is the result of an unhealthy behavior or whether depression causes the behavior.

Smoking: Previous research suggests depression is an established risk factor for smoking, with nicotine stimulating receptors in the brain which may improve mood in certain types of depression.4 The significance of nicotine use as a means of ameliorating depressive symptoms was supported by a longitudinal study examining smoking cessation. The study found that smokers with depressive symptoms in a control group continued to be highly symptomatic, while those who received nicotine replacement therapy did not have significantly higher depressive symptom scores relative to their non-depressed peers.5 Smokers have been found to be more likely than nonsmokers to experience daily symptoms of depression (29% vs. 19%).6 Notably as depressive symptom scores increase, the probability of smoking cessation decreases.7 Thus, depression is associated with an increased risk for smoking and, furthermore, may impede smoking cessation efforts.

Alcohol Consumption: Early onset of drinking has been reported to be associated with a range of problematic outcomes, including depressive symptoms.8 Assessing a clinical population, investigators reported a dynamic association between negative affect and lapses in sobriety following alcohol treatment.9 Specifically, these researchers found that changes in drinking following treatment were significantly associated with current and prior changes in negative affect, and, moreover, changes in negative affect were related to prior changes in drinking. These investigators concluded that negative affect and alcohol lapses were dynamically associated and indicate that assessing the relationship between negative affect and alcohol use could greatly decrease the probability of lapses from sobriety.9

Physical Inactivity: Physical inactivity and its strong correlate, obesity, have been identified as modifiable risk factors for depression.10 Researchers conducted a longitudinal, community-based study of depression and physical activity using data from the Canadian National Population Health Survey (NPHS), and found that, over time, major depression is associated with an increased risk of transition from an active to an inactive pattern of activity.11 These findings may have therapeutic implications, with physical activity reported to reduce depressive symptoms – even among individuals who are not clinically depressed.12

Sleep Disturbance: Depression appears to be associated with poor sleep throughout the lifespan.13, 14 In a cross-sectional study of 12- and 16-year old adolescents, after accounting for psychological comorbidity, sleep disturbance, such as nightmares, was associated with self-reported depression in adolescence (Coulombe et al. 2010). Some antidepressant agents are reported to commonly foster sleep disturbance.15

More detail on mental health/mental illnesses may be found at: or


  1. American Psychiatric Association. Quick Reference to the Diagnostic Criteria from DSM-IV. Washington, DC. American Psychiatric Press, Inc. 1994.
  2. NIMH Consensus Development Conference Statement. Mood disorders: pharmacologic prevention of recurrences. Am J Psychiatry. 1985;142:469-476.
  3. Sadock BJ & Sadock VA. Kaplan & Sadock’s Synopsis of psychiatry: Behavioral sciences/clinical psychiatry. (10th ed.).Philadelphia, PA: Lippincott, Williams, & Williams, 2007.
  4. Balfour DJ, Ridley DL. The effects of nicotine on neural pathways implicated in depression: a factor in nicotine addiction? Pharmacol Biochem Behav. 2000 May;66(1):79-85 (NIMH 1985)
  5. Korhonen T, Kinnunen TH, Garvey AJ. Impact of nicotine replacement therapy on post-cessation mood profile by pre-cessation depressive symptoms. Tob Induc Dis 2008;3:58.
  6. Sanderson Cox L, Feng S, Canar J, McGlichey Ford, M, Tercyak KP. Social and behavioral correlates of cigarette smoking among mid-Atlanta Latino primary care patients. Cancer Epidemiol, Biomark & Prev 2005;14:1976.
  7. Wiecha J, Lee V, Hodgkins J. Patterns of smoking, risk factors for smoking, and smoking cessation among Vietnamese men in Massachusetts (United States). Tob Control 1998;7:27-34.
  8. Trim RS, Schuckit MA, Smith TL. Predicting drinking onset with discrete-time survival analysis in offspring from the San Diego prospective study. Drug Alcohol Depend 2010;107:215-220.
  9. Witkiewitz K, Villarroel NA. Dynamic association between negative affect and alcohol lapses following alcohol treatment. J Consult Clin Psychol 2009;77:633-644.
  10. Ten Hacken NH. Physical inactivity and obesity: Relation to asthma and chronic obstructive pulmonary disease? Proc Am Thorac Soc 2009;6:663-667.
  11. Patten SB, Williams JV, Lavorato DH, Eliasziw M. A longitudinal community study of major depression and physical activity. Gen Hosp Psychiatry 2009;31:571-575.
  12. Conn VS. Depressive symptom outcomes of physical activity interventions: Meta-analysis findings. Ann Behav Med 2010;[Epub ahead of print].
  13. Coulombe JA, Reid GJ, Boyle MH, Racine Y. Sleep problems, tiredness, and psychological symptoms among healthy adolescents. J Pediatr Psychol 2010;[Epub ahead of print].
  14. Moreh E, Jacobs JM, Stessman J. Fatigue, function, and mortality in older adults. J Gerontol A Biol Sci Med Sci 2010 [Epub ahead of print].
  15. Bostwick JM. A generalist’s guide to treating patients with depression with an emphasis on using side effects to tailor antidepressant therapy. Mayo Clin Proc 2010{Epub ahead of print]