Friday, March 25, 2011

Here's a recent synthesis of studies on the course and remission rate for amphetamine, cannabis, cocaine and opioid dependence. Importantly they calculated remission rates using the assumption that drop outs from the studies were using and dependent (relapsed). This will result in an overly pessimistic view, since it is almost certain that not all of the study dropouts are still dependent. However, they do point that although addiction is frequently described as a "chronic, relapsing disease," there are surprisingly few studies that examine that.


Systematic review of prospective studies investigating 'remission' from amphetamine, cannabis, cocaine or opioid dependence.
Calabria B., Degenhardt L., Briegleb C. et al. Request reprint
Addictive Behaviors: 2010, 35, p. 741–749.

Review synthesises evidence on how many people recover each year (with or without treatment) from their dependence on stimulants, heroin-type drugs or cannabis, providing a baseline against which to assess improvement efforts.

Original abstract Aims To review and summarise prospective studies reporting on remission from dependence on amphetamines, cannabis, cocaine or opioids.

Methods Systematic searches of the peer-reviewed literature were conducted to identify prospective studies of people dependent on amphetamines, cannabis, cocaine or opioids like heroin, which followed them up for at least three years to investigate how many experienced remission from their dependence. Treatment trials were excluded, but studies of patients who entered treatment in the normal way were included along with non-treatment and general population samples. Remission was defined as abstinence from the drug of dependence or no longer meeting diagnostic criteria for drug dependence. The remission rate was estimated for each drug type, allowing pooling across studies with varying follow-up times. Searches were limited to publications between 1990 and 2009. Reference lists of review articles and important studies were searched to identify additional studies.

Results There were few studies examining the course of psychostimulant dependence that met inclusion criteria (one for amphetamines and four for cocaine). There were ten studies of opioid dependence, none of which were of general population samples, and three of cannabis dependence, all of which were of general population samples. Definitions of remission varied and most studies did not clearly assess remission from dependence. Where possible, data from the studies was used to calculate the annual proportion of patients who remitted, firstly as proportions of the patients who could be followed up. A figure for cannabis was not calculated. Based on a single US study of methamphetamine users, amphetamine dependence had the highest annual remission rate (0.45 or 45% a year no longer dependent), followed by opioid (0.22 or 22%) and cocaine dependence (0.14 or 14%). The single study (from the USA) of a general population sample of cocaine-dependent people found that 39% had remitted four years after initially surveyed.

However, studies reporting remission rates based solely on the followed-up sample inflate remission estimates, given that people who drop out are probably less likely to have remitted. The data was recalculated on the conservative assumption that every patient who could not be followed up was still dependent or had died dependent. These estimates differed quite markedly from the levels typically reported in papers. On this basis, remission rates were highest for cannabis dependence (0.17 or 17% a year no longer dependent) followed by amphetamine (just under 0.17 or 17%), opioids (0.092 or 9%) and cocaine dependence (0.05 or 5%).

Conclusions Despite the fact that drug dependence is commonly described as a "chronic" disorder, surprisingly few follow-up studies have documented the course of this disorder. In addition definitions used are often imprecise and inconsistent across studies. There remains considerable uncertainty about the longitudinal course of dependence upon these most commonly used illicit drugs. The limited prospective evidence suggests that 'remission' from dependence may occur relatively frequently but rates differ across drugs. Remission from amphetamine dependence was highest overall with almost one in two persons remitting during a given year; the conservative estimate of remission from amphetamine or cannabis dependence was one in six annually. Remission from opioid dependence ranged from one to two in ten each year; and remission from cocaine dependence ranged from one in twenty to one in eight. The findings of this review for cannabis are similar to the results of retrospective surveys (when people are asked to look back to recall whether they were dependent on the drugs rather than followed up) that have found cannabis to have the highest rates of cessation of use. The results are not consistent for opioid dependence, which has been found in retrospective surveys to have the lowest remission rates.

Last revised 16 March 2011

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