Depression (mood)
From Wikipedia, the free encyclopedia
Depression is a state of low mood and aversion to activity. While often described as a dysfunction, there are also strong arguments for seeing depression as an adaptive defense mechanism.
The Diagnostic and Statistical Manual of Mental Disorders defines a depressed person as experiencing feelings of sadness, helplessness and hopelessness. In traditional colloquy, "depressed" is often synonymous with "sad", but both clinical depression and non-clinical depression can also refer to a conglomeration of more than one feeling.
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[edit] Biology
Biological influences of depression are varied, but may relate to malnutrition, heredity, hormones, seasons, stress, illness, drug or alcohol use, neurotransmitter malfunction, long-term exposure to dampness and mold,[1] back injury, and to aerosol exposure.[2][3] There are also correlations between long term sleep difficulties and depression. Up to 90% of patients with depression are found to have sleep difficulties.[4]
[edit] Depression as a defense mechanism
A number of authors have suggested that depression is an evolutionary adaptation. A low or depressed mood can increase an individual's ability to cope with situations in which the effort to pursue a major goal could result in danger, loss, or wasted effort.[5] In such situations, low motivation may give an advantage by inhibiting certain actions. This theory helps to explain why depression is so prevalent, and why it so often strikes people during their peak reproductive years. These characteristics would be difficult to understand if depression were a dysfunction, as many psychiatrists assume.[5]
Depression is a predictable response to certain types of life occurrences, such as loss of status, divorce, or death of a child or spouse. These are events that signal a loss of reproductive ability or potential, or that did so in humans' ancestral environment. Depression can be seen as an adaptive response, in the sense that it causes an individual to turn away from the earlier (and reproductively unsuccessful) modes of behavior.
A depressed mood is common during illnesses, such as influenza. It has been argued that this is an evolved mechanism that assists the individual in recovering by limiting his/her physical activity.[6] The occurrence of low-level depression during the winter months, or seasonal affective disorder, may have been adaptive in the past, by limiting physical activity at times when food was scarce.[6] It is argued that humans have retained the instinct to experience low mood during the winter months, even if the availability of food is no longer determined by the weather.[6]
An alternative theory [7] posits that depression is a plea for help. However this view is not widely credited by evolutionary biologists: depression is observed in other species that are not social, and depression in humans is often actively hidden from others; even when it is apparent, it often fails to elicit a positive response.[8]
Milder depression has been associated with what has been called depressive realism, or the "sadder-but-wiser" effect, a view of the world that is relatively undistorted by positive biases.[9]
[edit] Psychiatric disorders
Episodes of depressed mood are a core feature of the following psychological disorders, as specified by the DSM-IV:
- Adjustment disorder with depressed mood
- Anorexia Nervosa
- Bipolar disorder
- Bulimia Nervosa
- Cyclothymia
- Depressive Disorder Not Otherwise Specified
- Dysthymia
- Major depressive disorder
- Postnatal depression
- Schizoaffective disorder
- Seasonal affective disorder (SAD)
[edit] See also
[edit] References
- ^ Edmond D. Shenassa, Constantine Daskalakis, Allison Liebhaber, Matthias Braubach, and MaryJean Brown (2007). "Dampness and Mold in the Home and Depression: An Examination of Mold-Related Illness and Perceived Control of One’s Home as Possible Depression Pathways". American Journal of Public Health 97 (10): 1893. doi:. PMID 17761567. PMC 1994167. http://www.ajph.org/cgi/content/abstract/97/10/1893.
- ^ Farrow, Alexandra (2003). "Symptoms of mothers and infants related to total volatile organic compounds in household products". Arch Environ Health 58 (10): 633–41. doi:. PMID 15562635.
- ^ Air fresheners can make mothers and babies ill, University of Bristol press release issued 19 October 2004
- ^ Roth T (2005). "Prevalence, associated risks, and treatment patterns of insomnia". J Clin Psychiatry 66 Suppl 9: 10–3; quiz 42–3. PMID 16336036.
- ^ a b Nesse R (2000). "Is Depression an Adaptation?". Arch. Gen. Psychiatry 57 (1): 14–20. doi:. PMID 10632228. http://www.google.com/url?sa=t&source=web&ct=res&cd=1&url=http%3A%2F%2Fwww-personal.umich.edu%2F%257Enesse%2FArticles%2FIsDepAdapt-ArchGenPsychiat-2000.pdf&ei=jk3MSovRNJ6qtgeY-6HtAQ&rct=j&q=%22is+depression+an+adaptation%22&usg=AFQjCNG_VSyM2WmMZebjLpzjgcj8CVluDQ.
- ^ a b c Why We Get Sick: The New Science of Darwinian Medicine, Randolphe M. Nesse and George C. Williams | Vintage Books | 1994 | ISBN 0-8129-2224-7
- ^ How Sadness Survived: The Evolutionary Basis of Depression, Marcello Spinella | Radcliffe Publishing | 2008 | ISBN 1846190134
- ^ Hendrie C A (2009). "Depression as an evolutionary adaptation: implications for the development of preclinical models.". Med. Hypotheses 72 (3): 342–347. doi:. PMID 19153014. PMID 19153014
- ^ Taylor, SE (1991). Positive Illusions: Creative Self-deception and the Healthy Mind. New York, NY, USA: Basic Books. ISBN 0465060536.
[edit] External links
- Depression at the Open Directory Project
- Depression Research News at ScienceDaily
- National Alliance on Mental Illness – Depression support, advocacy, and education
- National Depressive and Manic Depressive Association - National Depressive and Manic Depressive Association
- Stanford Depression Research Clinic
- Substance Abuse and Mental Health Services (SAMHSA) – United States Department of Health and Human Services (HHS)
- Doing Well – Depression self-assessment and information from the UK National Health Service
- Depression information from mental health charity The Royal College of Psychiatrists
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