For some reason many people are in denial about cannabis dependence and wish to assert that there is no such thing, or if there is, it is somehow of lesser importance than is dependence on other substances of abuse. There are many ways to assess importance of course. What gets me going, however, are the assertions about cannabis abuse and dependence that are informed by anecdote and personal experience with a handful of users instead of an understanding of the available evidence.
To provide a little context for todays' post, I took MarkH of denialism blog to task for his expression of what I viewed as standard cannabis science denialism a fair while ago. In a comment following his post, MarkH specifically identified nicotine withdrawal as being worse than cannabis withdrawal. This is the perfect setup since there are two recent papers which set out explicitly to test this hypothesis. Let us see what they found, shall we?
First off, what does cannabis withdrawal look like? As I've mentioned before the Diagnostic and Statistical Manual of Mental Disorders (DSM; current major version DSM-IV) employs generic substance abuse and dependence criteria for cannabis dependence. One of the ways the DSM gets revised over time is that researchers provide data and studies in-between revisions to attempt to refine and clarify diagnoses. The individual I most associate with the effort to describe the nature of cannabis dependence, and specifically withdrawal, is Alan J. Budney. He has a 2006 review of his (and others') work in this area and anyone who wishes to grapple with the consistency of findings and the subtleties of the subject samples under investigation should track back through the reviewed articles. For today, the important issue is that Budney proposes that a symptom list for cannabis withdrawal should be included in the next revision of the DSM as follows (from Table 1):
- Anger or aggression
- Decreased appetite or weight loss
- Sleep difficulties including strange dreaming
Less common symptoms/equivocal
- Depressed mood
- Stomach pain
Hmm. Very broadly consistent with symptoms established for other drugs of abuse, including nicotine. This brings us to the two papers comparing nicotine and cannabis withdrawal which have recently appeared; perhaps unsurprisingly, Budney is an author on each of these.
Vandrey RG, Budney AJ, Hughes JR, Liguori A. A within-subject comparison of withdrawal symptoms during abstinence from cannabis, tobacco, and both substances.
Drug Alcohol Depend. 2008 Jan 1;92(1-3):48-54. Epub 2007 Jul 23.
Budney AJ, Vandrey RG, Hughes JR, Thostenson JD, Bursac Z. Comparison of cannabis and tobacco withdrawal: Severity and contribution to relapse. J Subst Abuse Treat. 2008 Mar 12; [Epub ahead of print]
The first study, Vandrey et al, 2008, includes a relatively small sample (N=12) of cannabis/tobacco users (>6mo of 25 days/mo cannabis smoking, 10 tobacco cigarettes or more per day; all the usual exclusions of other issues). Importantly these individuals were not seeking treatment for either tobacco or cannabis use. The design was a series of blocks of Smoking As Usual (SAU) and the abstaining from cigarettes, cannabis or both for a 5 day interval. SAU for 9 days was interleaved between any of the abstinence intervals. Okay, so what did they find?
Fig. 2. Mean ratings for WSC items for which significant condition by day interactions were observed. Filled symbols indicate values significantly different from SAU. Subscripts designate differences by condition on a given study day (a = dual > cannabis and tobacco; b = dual and tobacco > cannabis; c = dual > cannabis;
d = dual > tobacco). Squares indicate abstinence from cannabis only, circles indicate abstinence from tobacco only, and triangles indicate abstinence from cannabis and tobacco.
Discontinuation of both substances seemed to cause the greatest degree of withdrawal, particularly in terms of anger, irritability and aggression on day 2. Cannabis discontinuation (alone) seemed to cause sleep disturbances for longer than did nicotine discontinuation (alone). Perhaps most strikingly, the discontinuation of cannabis (alone) or nicotine (alone) seemed to produce approximately equivalently severe withdrawal symptoms as rated by these dual-users.
The next study, Budney et al, 2008, included a larger samples of individuals who had recently attempted to quit tobacco (N= 54) or cannabis (N= 67). This was a retrospective method (unlike the above prospective method) to survey symptoms experienced during the subjects' prior attempts to quit substance use. Nevertheless the outcome was strikingly similar.
Fig. 1. Group mean severity scores for the WDS (refer to Y-axis scale on left side of figure) and individual symptoms on the Withdrawal Symptom Checklist
(refer to Y-axis scale on right side of figure). Asterisk indicates a significant difference between groups after controlling for age, gender, race, and Global Symptom Index score from the Brief Symptom Inventory in the linear regression models.
With the exception of appetite, craving and sweating symptoms, the severity of withdrawal symptoms was approximately equivalent across substances. This study also included the frequency of symptoms, i.e., the proportion of the sample which experienced each symptom.
Fig. 2. Percentage of participants from each group that reported each withdrawal symptom, i.e., scoring greater or equal to 1 on the 0-3 point Withdrawal
Checklist Scale. Asterisk indicates significant differences between groups on chi square analysis (p b .05).
As with symptom severity, the frequencies were similar. Except that cannabis withdrawal resulted in more individuals with irritability and decreased appetite while nicotine discontinuation resulted in more individuals with increased appetite and craving.
In total, these studies paint a picture in which the discontinuation of nicotine and cannabis produce withdrawal symptoms of relatively similar severity and in similar proportion.