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Addiction and addictive traits seem common amongst animals. A pubmed query shows it's been studied in everything from humans to worms.


Is there/was there something adaptive about addictive behaviour?

Alternatively, how it is that addictive behaviour survived/persists if it is not adaptive?

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    $\begingroup$ First, I think you are mixing up obsessive compulsive behavior with addiction, which isn't exactly the same. From a strictly biological perspective, addiction generally has to do with the reward pathways. What usually happens is the chemical that the organism becomes addicted to binds irreversibly to a receptor on a neuron. In order to stop the signal, the cell pulls down the receptor, as there are less receptors, more of the chemical is needed to induce the same response. Also the body tends to develop a physical need for that chemical and without it there are severe withdrawal consequences. $\endgroup$ – AMR Dec 16 '15 at 22:05
  • $\begingroup$ See this related ? Here. biology.stackexchange.com/q/36620/6061 $\endgroup$ – rhill45 Dec 17 '15 at 1:36
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Albeit used in the keywords of the paper, feather pecking is not an addiction, but normal behavior turned pathological in artificial (overcrowded) environments.

Addiction typically arises through overstimulation of reward centers in the brain, most notably the dopaminergic pathways involving the nucleus accumbens. Massive dopamine release, e.g. through cocaïne or meth intake, results in euphoria (Wise & Bozarth, 1985). When the drug's effects wear off it is followed by the 'crash', characterized by dysphoria and a longing for more drugs (CSAT, 1999). Gambling addiction works much in the same way.

Addiction develops because of an interplay of dependence and tolerance. Dependence is caused by downregulation of dopaminergic responses in the reward centers. Notably, dopamine receptors are downregulated when dopamine agonists like stimulant drugs of abuse are chronically administered. Downregulation of dopaminergic responses causes the physiology of the reward pathway to adapt to the presence of dopamine agonists. While the drug is in the system, everything is OK. However, once the levels of the dopamine agonist wears off, the body enters a state of lack of dopaminergic responses, causing dysphoria and depression. Tolerance develops as the liver and other tissues start breaking down the drug more efficiently due to upregulation of the necessary catabolic enzymes. Hence, more of the drug is needed, and the user becomes more and more tolerant. The interplay of dependence and tolerance form the dreaded vicious, downward spiral of addiction.

The reward centers have been crucial in evolution, as they provide motivation to vital acts of life, including eating and sex (University of Colorado, Boulder). Without a proper reward system, why eat or reproduce? However, drugs and other addictive acts such as gambling also activate the reward system.

Highly purified drugs such as crystal meth and cocaïne result in massive dopamine release that is unparalleled by normal physiologic processes such as eating. Before the occurrence of stimulants and things like gambling, the reward system was nothing but essential to life and evolution. Now, things are different and man needs to adapt to these novel, artificial pleasures in life.

References
- Treatment Improvement Protocol (TIP) Series, No. 33. Center for Substance Abuse Treatment. Rockville (MD); 1999
- Wise & Bozarth, Psychiatr Med (1985); 3(4): 445-60

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Although addiction as a coping mechanism may help in the short term. Ie.preventing a depressed person from killing themselves through temporary relief of symptoms. In the long run addiction causes many more problems then it solves. The type of addiction also needs to be considered. Many alcoholics can go years before health and financial problems begin to cause trouble. Enough time to raise a family. Possibly the reason addiction genes haven't been removed from the pool. If you look at possibility the most extreme form of addiction, wires directly into the pleasure center of the brain. You see how completely maladaptive it can be. The monkeys will sit and press the button over and over. They neglect grooming behavior, other external stimulation,food and water. Loosing interest in anything beyond the pleasure button. Eventually succumbing to exhaustion. If allowed they will continue pushing the button and die as a result. This is an extreme case because with electronic stimulation the regular negative feedback that results from overstimulation of the pleasure centers appears to be absent. chemical stimulation of the pleasure centers causes tolerance and the feeling becomes harder to obtain the more one uses. Although many addicts chase the high until it kills them as well.

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    $\begingroup$ can you add some references to your answer? we always appreciate external references to questions and answers on BiologySE - thanks! $\endgroup$ – Vance L Albaugh Nov 4 '16 at 0:32

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