Sleep Time Differs among People who Co-Use Cocaine and Cannabis Compared to People who Only Use Cocaine

Abstract

Objective:

People who use cocaine experience numerous sleep problems and often use cannabis to mitigate these problems. However, co-using cocaine and cannabis may result in worse sleep outcomes when compared to using cocaine only. The current study examined group differences in subjective sleep outcomes among people who use cocaine and people who co-use cocaine and cannabis.

Methods:

Participants were 82 individuals with cocaine use disorder who were enrolled in a randomized clinical trial for cocaine treatment. Sleep outcomes, assessed at baseline prior to treatment, were measured with the Saint Mary’s Hospital Sleep Questionnaire and included total sleep time, perceived sleep quality, difficulty falling asleep, and daytime alertness. Analysis of covariance and Kruskal-Wallis tests were used to compare sleep outcomes between participants with urine samples that tested positive for both cocaine and cannabis at baseline, those who tested positive for cocaine only, and those who tested negative for all drugs.

Results:

Total reported sleep time was highest among those with a drug negative urine, followed by those with a cocaine positive urine and those who tested positive for cocaine and cannabis. There were no differences in perceived sleep quality, difficulty falling asleep, or daytime alertness between groups.

Conclusions:

People who co-use cocaine and cannabis may report reduced sleep time relative to those who only use cocaine. Co-use of cannabis may exacerbate sleep difficulties in people who use cocaine by decreasing total sleep time, although it is important to note that the groups each reported similar sleep quality. Implications for treatment and directions for future research are discussed.

INTRODUCTION

In 2018, approximately one million people in the U.S. were diagnosed with a cocaine use disorder (CUD).¹ People with a CUD who aim to abstain from cocaine are challenged with withdrawal symptoms that can manifest within days of cessation and persist for weeks.² In particular, discontinuing cocaine use is associated with sleep disturbances that may exacerbate cravings and increase the likelihood of relapse.^3-5 Many people who use cocaine also use cannabis,⁶ commonly as a sleep aid that is associated with subjective reports of improved sleep quality.^7-8 However, people who chronically use cannabis may experience changes in sleep duration and sleep latency.⁹ The similar sleep disturbances produced by these two substances suggests combining cocaine and cannabis may exacerbate sleep problems and influence treatment outcomes. This issue has received little attention in the literature. Understanding sleep differences between people who only use cocaine and those who co-use cocaine and cannabis can inform sleep-related needs for those entering drug treatment. Therefore, the current study aimed to examine group differences in subjective sleep outcomes related to total sleep time and perceived sleep quality among people who use cocaine and people who co-use cocaine and cannabis prior to enrolling in treatment for cocaine use disorder.

Cocaine Use and Sleep Outcomes

Existing research demonstrates the negative effects of cocaine use on sleep outcomes.^9-10 Chronic cocaine use influences dopamine reuptake, which can increase sleep onset latency, decrease total sleep time, and suppress REM sleep.^11-12 For cocaine users who seek treatment or attempt to stop their use, these sleep complications intensify during early abstinence.¹³ Polysomnographic (PSG) reports show after only two days of cocaine cessation, cocaine users begin experiencing increased sleep onset latency and slow wave sleep, and decreased sleep efficiency and total sleep time.¹⁰ These sleep complications may lead cocaine users to experience physiological symptoms comparable to insomnia,¹¹ which may affect recovery efforts. Despite physiological sleep changes, cocaine users experiencing withdrawal typically do not report problems with sleep latency, total sleep time, or sleep satisfaction.⁹ For example, Hodges and colleagues found chronic cocaine users accurately reported their total sleep time after 1 week of abstinence but overreported their total sleep time after 2 weeks of abstinence.¹⁴ This phenomenon is known as “occult insomnia,” where there is a discrepancy between objective and subjective reports of sleep quality among chronic cocaine users.¹⁴ The quantitative and qualitative reports of sleep quality appear similar to those of healthy sleepers only after several weeks of continued cocaine abstinence.¹³

Sleep disturbances and misperceptions after cocaine cessation have implications for treatment outcomes. Scholars have proposed that sleep disturbance is a risk factor for relapse,¹⁵ as reduced sleep may lead to greater vulnerability for cocaine craving. Pre-clinical evidence suggests that sleep reduction impedes the extinction of previous cocaine-environment conditioning in rats.^3-4 Further, sleep disturbance may account for the changes in dopamine receptor availability that have been associated with increased risk for relapse among cocaine users.¹⁶ In addition to exacerbating cravings, sleep changes during early abstinence may also inhibit cognitive functioning that can influence substance use treatment outcomes. For example, sleep deficits among cocaine users negatively affect learning processes such as memory consolidation and motor sequence tasks.^17-19 Based on this evidence, improving sleep may be a helpful method of promoting abstinence and recovery among those seeking treatment. Therefore, it is important to broaden our understanding of factors that may exacerbate sleep disturbances among cocaine users seeking treatment.

Cannabis Use and Sleep Outcomes

One way that sleep concerns are managed by people who use cocaine is by using cannabis. In addition to improving subjective reports of difficulty falling asleep, cannabis use has been cited as a therapeutic way to reduce cocaine-related cravings and symptoms of paranoia, fear, distrust, and aggressiveness.¹¹ However, daily cannabis use produces a decrease in total sleep time and an increase in sleep onset latency on PSG results, particularly if one attempts to reduce cannabis use.^20-21 Therefore, chronic cannabis use can produce similar sleep consequences as chronic cocaine use. Angarita and colleagues describe this conundrum as a “catch-22,” where cannabis may be used to facilitate falling asleep but over time, increased cannabis use can worsen symptoms of insomnia.⁹ These sleep problems may then contribute to greater cannabis use to fall asleep,¹² creating a cycle of increasing drug use and worsening sleep problems.

Cocaine and Cannabis Co-Use and Sleep Outcomes

Cannabis use among cocaine users is common, with an estimated 64% of cocaine users reporting concurrent use of cannabis.⁶ However, there is no research examining how co-use of cocaine and cannabis influences sleep outcomes. Evidence suggests that cannabinoids, chemical compounds present in cannabis, may provide a therapeutic benefit to reducing cocaine-induced anxiety and seizures.²² However, the similarities in sleep impairment shared by users of cocaine and cannabis suggest further research is needed in order to determine whether co-users of cocaine experience poorer sleep outcomes, which may impact their risk for relapse and treatment retention. Therefore, the current study seeks to examine group differences in subjective sleep outcomes based on biological indicators of cocaine use or cocaine and cannabis co-use (i.e., cocaine positive urine samples or cocaine and cannabis positive urine samples, compared to those who provided urine samples that tested negative for all drugs).

METHOD

Data for the current study were derived from baseline measures of an ongoing randomized clinical trial examining health outcomes associated with reductions in cocaine use (NCT03224546). In order to be eligible, participants had to be 18-65 years old, provide a cocaine positive urine sample during screening, currently meet DSM-5 criteria for CUD, have a urine drug screen that is positive for cocaine during initial screening, be seeking treatment for cocaine use, and be able to commit to a 12-week intervention and 24-week follow-up. All data for this analysis originate from a single separate “baseline” visit that occurred at the end of all screening for the study, immediately prior to each participant’s enrollment in the 12-week intervention.

Measures

Cocaine and Cannabis use:

Participants completed a urine drug test using CLIA Waived, Inc. 14 Panel Instant Drug Test Cup, which screened for several drugs, including cocaine, cannabis, amphetamines, opiates, and benzodiazepines. Testing was completed in a research laboratory at the University of Kentucky in Lexington, KY, and each test outcome was verified by two separate research staff. Urinalysis indicated the presence of three groups. Participants with CUD who tested positive for cocaine at baseline were defined as the cocaine (COC) group, while participants who tested positive for cannabis and cocaine were defined as the COC+THC group. Participants with CUD who tested negative for both cocaine and cannabis were defined as the NONE group. Three individuals tested positive for cannabis only; due to small sample size, these participants were removed from further analysis. Only three individual participants tested positive for one other substance in addition to cocaine and/or cannabis. One COC and one COC+THC participant each tested positive for tricyclic antidepressants, and a separate COC participant tested positive for amphetamines.

Sleep Measures:

The St. Mary’s Sleep History Questionnaire (SMHSQ),²³ a self-report measure of perceived sleep outcomes, assessing sleep from the day prior. Select items were used to assess the following:

Total Sleep Duration:

Participants were asked to report their total sleep duration the day prior to their assessment. Participants were asked two separate questions: “How much sleep did you have: Last night? During the day, yesterday?” Responses for these two items were totaled to produce a measure of total sleep time in minutes. Both sleep from the previous night and during the previous day were used, as many participants reported working overnight and sleeping during the day.

Daytime Alertness:

Participants were asked, “How clear-headed did you feel after getting up this morning?” Responses ranged from 1=still very drowsy indeed to 6=very alert.

Sleep Quality:

Participants were asked to rate how well they had slept the previous night, with responses ranging from 1=very badly to 6=very well.

Difficulty Falling Asleep:

Participants were asked, “How much difficulty did you have in getting off to sleep last night?” Responses ranged from 1=none or very little to 4=extreme.

Demographic Variables:

Participants were asked to report their race, age, years of education, and gender using the Addiction Severity Index, Lite (ASI-L).²⁴ The ASI-L was also used to determine number of days in the last 30 days that participants used cocaine, as well as the number of days they used cannabis. DSM-5 criteria were used to determine the number of CUD symptoms each participant endorsed. Number of criteria were totaled to indicate level of CUD severity for each participant. Differences in these demographic variables between COC and COC+THC participants were examined to determine potential covariates for the main analyses.

Data Analysis

Participant descriptive statistics were calculated to compare characteristics of the three groups. Chi-square analyses and ANOVA were used to examine group differences in categorical and continuous descriptive variables. Non-parametric Kruskal Wallis tests were used to compare differences in ratings of sleep quality, daytime alertness, and difficulty falling asleep due to these variables being measured on an ordinal scale. Analysis of covariance (ANCOVA) was used to compare mean total sleep time between the three groups. Statistical significance was set at p<0.05.

RESULTS

Participants ranged in age from 23 to 61 years old. People who tested positive for neither cocaine nor cannabis (NONE) reported lower past 30-day cocaine use compared to COC and COC+THC (Table 1). Further, age differed significantly between the three groups, with COC+THC having the lowest average age of 45 years (F=10.80, p<0.001). Total sleep time ranged from 100 minutes to 1070 minutes among participants. An ANCOVA was conducted to determine differences in total sleep time between COC, COC+THC, and NONE, controlling for age. Data screening for outliers led to the removal of two cases in the COC group with total sleep times greater than 1000 minutes from final analysis. Prior to completing analysis, tests for normality of standardized residuals and interaction between the covariate and IV were conducted. The Shapiro-Wilk test for normality of overall data residuals showed data was approximately normally distributed (p=0.136). The interaction between age and group on the total sleep time outcome was not significant (p=0.781), so the analysis was conducted examining only main effects.

Table 1.

Descriptive differences among participants based on whether they tested positive for cocaine (COC), cocaine and cannabis (COC+THC), or neither (NONE).

	NONE (n=10)			COC (n=49)			COC+THC (n=20)			p- value
	Mean	Range	%	Mean	Range	%	Mean	Range	%
African American			90%			79.6%			85.0%	0.69
Age	50.70	23-65		55.04	38-65		45.00	30-61		<0.01*
Years of Education	13.00	11-16		12.68	8-18		12.20	10-15		0.40
Male			90.0%			59.2%			70.0%	0.16
CUD Severity	7.33	4-11		7.68	4-11		8.53	6-11		0.22
Cocaine Use- last 30 days	5.70	0-21		13.94	0-30		14.60	1-30		0.019*
Cannabis Use- last 30 days	0.20	0-1		0.63	0-8		13.85	0-30		<0.01*

After adjusting for age (past 30 day use of cocaine and cannabis were not used as covariates given high overlap with urinalysis group), a comparison of group means showed participants in the COC+THC group reported the lowest total sleep time, followed by COC participants, and participants in the NONE group had the greatest total sleep time (Table 2). The relationship was statistically significant with a medium effect size [F(2, 73)=3.33, p=0.041, partial eta²=0.084]. Post-hoc analysis showed that the mean total sleep time was significantly lower for the COC+THC group compared to the NONE group, with a difference of approximately 133 minutes (p=0.038). The differences in total sleep time between COC+THC and COC was 64 minutes and between COC and NONE was 69 minutes; however, neither of these comparisons reached statistical significance. Kruskal Wallis tests showed the median sleep quality rating for all groups was 4 (“fairly well”) and the median daytime alertness score was 4 (“fairly clear-headed”). The NONE group had a difficulty falling asleep median score of 1.5, which fell between “none or very little” and “some;” however, it did not differ significantly from the other two groups’ median score of 1 (Table 2).

Table 2.

ANCOVA and Kruskal Wallis tests examining baseline differences between sleep outcomes among participants who tested positive for used cocaine only (COC) and cocaine and cannabis (COC+THC), or neither (None)

	None (n=10)		COC (n=47)		COC+THC (n=20)
	Adjusted Mean	95% CI	Adjusted Mean	95% CI	Adjusted Mean	95% CI	F	p- value
Total Sleep Time (minutes)	528.71	445.68, 612.26	459.52	419.46, 499.58	395.40	331.46, 459.33	3.33	0.041
	Median	Range	Median	Range	Median	Range	H	p- value
Sleep Quality	4	3-6	4	1-6	4	3-6	0.498	0.780
Difficulty Falling Asleep	1.5	1-2	1	1-4	1	1-3	0.061	0.970
Daytime Alertness	4	3-5	4	1-6	4	1-6	1.592	0.451

DISCUSSION

The current study examined differences in total sleep time and perceived sleep quality among people with CUD who were entering treatment for cocaine cessation. Each group was comparable with regards to race, sex, education level, and number of CUD criteria reported. The rates of cocaine use were also comparable between the COC and COC+THC groups, averaging 14 days of use in the past 30. The NONE group had an average of 5 days of cocaine use in the last month; however, overall CUD criteria were similar to COC and COC+THC groups, indicating that symptom burden was similar despite fewer total days of cocaine use. Cannabis use varied significantly as would be expected, with COC+THC participants reporting an average of 14 days of use in the last month compared to less than one day among COC and NONE participants. Participants who co-used cocaine and cannabis reported sleeping more than two hours less on average than those who did not test positive for cocaine or cannabis, and approximately one hour less than those who tested positive for cocaine only. This suggests co-use of cocaine and cannabis may exacerbate sleep problems more than cocaine use alone, contrary to intended mitigation of sleep problems that many co-users seek.^6-8

Our findings indicate differences in total sleep time that can have clinically significant implications for cocaine use treatment. A sleep difference of at least one hour can be associated with decrements in cognitive behavioral performance,²⁶ whereas better sleep improves one’s attention, mood, and memory to successfully engage in treatment.¹³ Less sleep time may also place those who use COC+THC at higher risk for craving cocaine,^3-5 which raises concerns for reduction efforts as sleep disturbances can worsen during early abstinence.⁹ One study showed that average total sleep time decreased from approximately 380 minutes to 340 minutes over the course of the first few weeks of abstinence from cocaine use.²⁷ Our results suggest that those who use COC+THC already have a lower baseline of total sleep time compared to those who use cocaine only, and therefore may experience even less sleep as they attempt to reduce or abstain from cocaine use. Further, those who use COC+THC prior to cocaine treatment enrollment may increase cannabis use over the course of treatment to compensate for decreased cocaine use. The combined impact of cocaine reduction and potential increases in cannabis use may continue to compound sleep problems and influence treatment success.^10,20-21

Our results showed people who use COC+THC may not perceive their sleep to be worse than people with CUD who do not frequently use cannabis, despite potential differences in total sleep time. All groups perceived their sleep to be of similar quality, reported little difficulty falling asleep, and reported feeling alert during the day regardless of urinalysis results. Our results are consistent with prior research showing discrepancies in total sleep time and perceived sleep quality among people who use cocaine.^14,19,25 This finding suggests COC+THC use increases risk for occult insomnia. It may be of benefit to consider addressing healthy sleep during the beginning of CUD treatment regardless of participant self-reports of sleep quality, particularly among people who report co-use of cannabis. There are numerous nonpharmacological techniques that could be incorporated into substance use treatment to aid in sleep.²⁸ For example, Britton and colleagues demonstrated that a mindfulness meditation intervention improves sleep duration among people in treatment for substance abuse disorder.²⁹ Promising pharmacological interventions such as modafinil have also demonstrated improvements in sleep time and quality among people with CUD.¹³ Recent work suggests cannabidiol, one of the many chemicals found in cannabis, may have therapeutic effects in reducing cocaine-related anxiety and seizures.²² However, our current findings suggest cannabis use may not aid in sleep duration among chronic cocaine users. It may be that some of the other compounds found in cannabis are a detriment to sleep over time while other compounds such as cannabidiol have other therapeutic benefits. This prompts the need for further study on the effects of cannabidiol on sleep among people who use cocaine.

CONCLUSIONS

These preliminary results from baseline data of a randomized control trial indicate a critical intervention point for those who co-use cocaine and cannabis. There are also limitations that raise important future directions. First, the sample sizes of the three groups were relatively small and uneven, which may suggest the need to interpret our study results with caution. Second, although there is evidence to suggest people who use cocaine also use cannabis to mitigate the effects of cocaine on sleep, the current study did not measure whether participants used the two substances in the same day or at the same time. The use of biological confirmation to demonstrate recent cannabis and cocaine use has methodological strengths over self-report measures. However, the urinalysis used for the current study was unable to provide a quantitative estimate of THC levels. Therefore, we cannot say how much THC was in each COC+THC participant’s system at baseline, which likely would impact their sleep reports as well. Future research on sleep outcomes should incorporate assessment of simultaneous use of cocaine and cannabis (i.e., in the same day or at the same time) in addition to quantitative estimates of THC levels in urinalysis. Relatedly, the small number (n=3) of participants who tested positive for THC but not cocaine precluded us from comparing THC only to COC or COC+THC. Further study is needed to determine how the combined effect of cocaine and cannabis on sleep as determined by urinalysis differs from cannabis alone.

Another limitation is the current study used subjective measures of total sleep time and sleep quality. These estimations may be less accurate than polysomnography (PSG) results; however, evidence suggests subjective and objective measures of sleep highly correlate during the first week of withdrawal.¹⁴ Because the current study assessed sleep outcomes at baseline and prior to cocaine cessation efforts, the reported total sleep times may align with PSG results. Future research should utilize objective measures of sleep to determine whether total sleep time varies between COC and COC+THC over the course of abstinence. The current study is also limited in that it does not assess other objective measures of sleep quality, such as sleep architecture. Evidence indicates that both chronic cocaine use and chronic cannabis use impact sleep stages, including time spent in slow wave sleep and REM sleep stages.^9,11-12 Given potential differences in total sleep time indicated by the present findings, further examination of how cocaine and cannabis co-use may also affect other objective features of sleep quality using PSG assessment is warranted.

Lastly, this study is cross-sectional and does not examine changes in sleep throughout the course of treatment. However, in demonstrating potential differences in total sleep time at treatment enrollment, our study highlights a plausible direction for future research by monitoring differences in sleep depending on frequency of cocaine use and whether one co-uses cocaine and cannabis. Further investigation is warranted to identify the extent to which COC+THC users are at greater risk for cocaine use relapse due to sleep disturbances.

Highlights.

• We compared sleep outcomes in people who used cocaine only or cocaine and cannabis

• Total sleep time differed across the groups

• Those with drug negative urine samples reported greatest total sleep time

• Those with cocaine positive samples slept more than those with cocaine/cannabis positive samples

• There were no differences in perceived sleep quality across groups