These data provide compelling evidence that abrupt cessation of heavy MJ use is associated with sleep disturbances and that these disturbances progress over the first two weeks of abstinence. This study also yields a number of important findings that can direct future research. First, abstinent MJ users show declines in TST, SEff%, and REM/%TST and increases in WASO and PLM across abstinence. Thus, the sleep PSG variables indicate more disrupted sleep across abstinence. Nevertheless, it is unclear whether this change relates to abstinence from MJ or reflects a return to the individual’s pre-MJ smoking sleep pattern. Second, the data show no noteworthy improvement in any PSG measure of sleep. Third, we report potentially important sex and age-related associations, and MJ dose-related effects on mean change in PSG indices during MJ abstinence. Finally, these data are important because there is limited PSG data available in this young adult age demographic.
Except for SWS, our results demonstrate a negative trend during the 14 days of abstinence for all our sleep indices. Our finding that REM/%TST decreases during abstinence is not supported by others who find increased REM/%TST during a shorter abstinence interval than ours (1 to 3 days) after high oral THC administration (11
). Based on normal Horne-Ostberg Index (morningness/eveningness) questionnaire screening and normal REM latencies, we do not believe that decreased REM/%TST is due to confounders such as a phase delay. Since MJ is a REM suppressant when given acutely, it is possible that others found an initial rebound increase of REM early in abstinence because they administered high levels of oral THC. We also found significant declines in TST, SEff, and an increase in WASO not reported in the literature previously. Although no PSG studies of 14-day abstinent MJ users are available for comparison, cocaine users abruptly discontinuing use for 23 days also show reductions in TST and more WASO (35
). Thus, PSG changes seem to occur across relatively long periods (at least 2 weeks) after either cocaine or MJ discontinuation. Although SWS/%TST increased marginally in a positive direction, both values were clinically abnormal [Night 1 SWS/%TST = 7.0 (5.6) versus Night 13 SWS/%TST = 8.1 (5.5)]. The mean nightly sleep duration reported by this MJ cohort prior to entering the study was 6.5 hours; therefore, one must consider that the small increase of SWS/%TST may have resulted from SWS rebound resulting from chronic sleep deprivation, which occurs preferentially over REM sleep.
Women had more TST, REM sleep and PLMAs than men during MJ abstinence. The origins of these differences between our women and men are unclear. We determined that these differences were not due to sex differences in MJ use history. Others have reported greater SEff in women than men (32
) and have attributed this to more sleep-related respiratory disturbance in men. We excluded individuals with an AHI of >10 so we do not believe this was a major determinate of our sex-related PSG differences. Although specific aspects of sleep have been found to be influenced by menstrual cycle (36
), because we had only five women in our sample and they were in different stages of their menstrual cycle, no meaningful patterns could be detected. Of interest, other investigators reported that abstinent cocaine using women, in similar stages of their menstrual cycle, show more TST than men, which is consistent with our observation in abstinent MJ users (35
). Future studies should explore this relationship systematically.
Despite our restricted age range of 18 to 30 years old, SEff declined per year of age and WASO increased per year of age. While age-related PSG differences have been well studied in the elderly, there has been a paucity of sleep research on non-clinical young adults, (31
), and no research has examined the interaction between MJ use and age on PSG. Expanding this research to older MJ users would help clarify the modifying role of age on sleep disturbance in abstinent MJ users.
Our MJ users report less craving and fewer withdrawal symptoms during MJ abstinence relative to baseline. We posit that craving and withdrawal symptoms were negligible because of the lack of “drug-taking” cues in our inpatient unit. Notwithstanding deteriorations in specific sleep indices, our MJ users do not report significantly less sleep satisfaction over time. This paradoxical finding is also reported in abstinent cocaine users and may be associated with dysregulation of the homeostatic sleep drive, the drive that translates increasing time awake into drive for sleep (37
). This same mechanism may also explain our current findings in MJ users. Moreover, this dysregulation could potentially be a general factor-reflecting disturbance of this basic homeostatic drive that may promote recurrent drug use and relapse (38
We also found that higher amounts of MJ used were associated with greater increases in PLMs during the 14 days of abstinence. Four of our 18 MJ users (22%) developed a PLM index >10 by Night 13 of abstinence (). All of these MJ users smoked >85 joints per week (the group median). Moreover, longer duration of MJ use was associated with the development of more PLMs over time. There are no well-documented reports of normal PLMs in young adults, especially controlling for sleep-disordered breathing, as was done in this study. In normal adolescence the PLM index is usually <10 (39
). There have been antidotal reports that MJ may actually reduce PLMs in certain individuals. Perhaps our MJ users who developed PLMs already had PLMs and their MJ use had reduced their symptoms to the point where they were not observed during the first few days of the study. Although we attempted to gather a detailed history of chronic sleep disturbances including PLM symptoms, it is possible that our MJ users denied PLM symptoms because their leg movements were masked by years of heavy MJ use. This could explain why PLMs increased over time as the levels of MJ decreased (see ).
We were able to detect significant negative change in PSG indices with time in our MJ group. However, for those PSG variables that failed to show any change during abstinence, it may be that the effects were of smaller magnitude and our sample size was not large enough to detect these effects. The results of this study will not generalize to all users of MJ since our specific sample of MJ users was primarily young, reported sleep disturbance when discontinuing smoking MJ in the past, and some smoked large amounts of MJ. We studied only MJ users who reported sleep disturbance when attempting to discontinue MJ use in the past because, as a first step, we were most interested in our ability to determine if objective PSG abnormalities were present and because we believed this group would be the most similar to clinically relevant treatment seekers.
We acknowledge that it would have been better to start collecting our PSG data during a MJ use condition. This change in study design may have reduced some of the variability in our PSG data, especially during the initial PSG study nights. Nevertheless, our entire MJ group reported using MJ within 48 hours of admission and our results were unaffected after we controlled statistically for time since last use.
We believe our findings suggest potentially important associations that deserve further investigation. PSG evidence of sleep disturbance increased as levels of THC-COOH decreased, suggesting an association between declining levels of MJ and increasing sleep disturbance. However, it is impossible to determine if we may have unmasked an underlying sleep disorder, rather than a withdrawal syndrome. Although we screened very carefully for any history of symptoms suggesting a pre-existing sleep disorder and excluded participants for any abnormal initial PSG findings, it is possible that our MJ users were unable to recollect the severity of their past sleep problems because of their extensive history of MJ use. Furthermore, we also need to consider that anticipation about leaving the sleep unit could have affected some of the PSG findings on Night 13. We acknowledge these short-comings; nevertheless, this study was conducted as an initial step and is one of the few that carefully measures objective PSG sleep parameters during an extended period of abstinence.
Investigating sleep disturbance in MJ users provides evidence-based knowledge for developing prevention programs and non-pharmacological and pharmacological treatment interventions targeting the underlying mechanisms of sleep dysfunction associated with the discontinuation of daily, heavy MJ use or with other abused substances. Specifically, these findings also demonstrate that the development of specific sleep impairments may be age and sex specific. Thus, treating clinicians may need to modify their treatment programs for MJ cessation–related sleep disturbance for different ages and sexes. With treatment of the sleep dysfunction, any potentially adverse functioning consequences (i.e., poor cognitive function, daytime sleepiness) should also improve, resulting in better overall treatment outcomes in heavy MJ users.