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Abstract
Drug addiction is a chronically relapsing disorder that has been characterized by (1) compulsion to seek and take the drug, (2) loss of control in limiting intake, and (3) emergence of a negative emotional state (eg, dysphoria, anxiety, irritability) reflecting a motivational withdrawal syndrome when access to the drug is prevented. Drug addiction has been conceptualized as a disorder that involves elements of both impulsivity and compulsivity that yield a composite addiction cycle composed of three stages: ‘binge/intoxication', ‘withdrawal/negative affect', and ‘preoccupation/anticipation' (craving). Animal and human imaging studies have revealed discrete circuits that mediate the three stages of the addiction cycle with key elements of the ventral tegmental area and ventral striatum as a focal point for the binge/intoxication stage, a key role for the extended amygdala in the withdrawal/negative affect stage, and a key role in the preoccupation/anticipation stage for a widely distributed network involving the orbitofrontal cortex–dorsal striatum, prefrontal cortex, basolateral amygdala, hippocampus, and insula involved in craving and the cingulate gyrus, dorsolateral prefrontal, and inferior frontal cortices in disrupted inhibitory control. The transition to addiction involves neuroplasticity in all of these structures that may begin with changes in the mesolimbic dopamine system and a cascade of neuroadaptations from the ventral striatum to dorsal striatum and orbitofrontal cortex and eventually dysregulation of the prefrontal cortex, cingulate gyrus, and extended amygdala. The delineation of the neurocircuitry of the evolving stages of the addiction syndrome forms a heuristic basis for the search for the molecular, genetic, and neuropharmacological neuroadaptations that are key to vulnerability for developing and maintaining addiction.

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Some suggested reading

20 Flaws in Study Finding No Health Problems in Adult Males Who Were Chronic Marijuana Users as Teens, Young Adults2015
High potency cannabis - a risk factor for dependence, poor psychosocial outcomes, and psychosis, Hall, Degenhardt, BMJ 2015

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Date: May 27, 2015
Source: American Association for Clinical Chemistry (AACC)
Summary:
Cannabis plus alcohol is one of the most frequently detected drug combinations in car accidents, yet the interaction of these two compounds is still poorly understood. A study shows for the first time that the simultaneous use of alcohol and cannabis produces significantly higher blood concentrations of cannabis's main psychoactive constituent, THC, as well as THC's primary active metabolite than cannabis use alone. For complete article go to…. View article here

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Opium use and mortality in Golestan Cohort Study: prospective cohort study of 50 000 adults in Iran

BMJ 2012; 344 doi: Click Here (Published 17 April 2012)
Cite this as: BMJ 2012;344:e2502  

Conclusion: Opium users have an increased risk of death from multiple causes compared with non-users. Increased risks were also seen in people who used low amounts of opium for a long period and those who had no major illness before use

To read full article go to Click Here