Theses Doctoral

Marijuana, Methamphetamine, and Oxycodone: A multilevel approach to understanding drug effects

Keith, Diana

Drug use and abuse remains an important public health problem in the United States. In particular, there has been considerable recent concern regarding the illicit use of marijuana, methamphetamine, and prescription pain relievers. However, several important gaps remain in our knowledge of these drugs. The current studies aim to address three of these gaps. Further, the present studies utilized a translational, multilevel approach in order to better understand substance use as a whole. First, although there have been a number of studies examining marijuana use in college students, there is a lack of information regarding the consequences of marijuana and alcohol co-use, as well as the relationship between marijuana use and mental health and stress. Study 1 examined the relationship between frequency of marijuana use and other substance use, binge drinking, negative consequences associated with drinking, mental health problems, and stress. Results show that students who reported more frequent marijuana use were more likely to use all other substances, binge drink, and have drinking-related encounters with the police. Frequency of use was also related to diagnosis and/or treatment for major depression and substance use disorders. On the other hand, any marijuana use was associated with greater likelihood of experiencing a number of negative consequences from drinking, and diagnosis or treatment for anxiety disorders. Marijuana was not related to stress. This data contributes to the field by indicating that marijuana use is indeed related to mental health among this population. This has important implications for university administrators and health professionals. Study 2 was the first empirical investigation of the acute effects of marijuana during simulated night shift work in marijuana users. Night shift workers are particularly susceptible to performance impairments and often use drugs in order to manage their sleep-wake cycles. The results indicated that smoked marijuana attenuated performance and mood disruptions during simulated night shift work. This data furthers the database by indicating that marijuana has cognitive-enhancing effects under certain conditions. Additional research will be needed in order to determine whether these effects were caused by circadian modulation of the stimulant-related effects of marijuana, or by residual effects on improved sleep. Another important gap addressed by the present studies is the dearth of empirical information regarding the effects of methamphetamine when combined with oxycodone. Study 3 addressed this gap by beginning a systematic investigation of this drug combination utilizing a pre-clinical model with a wide range of cognitive and behavioral measures. Results indicated that the drug combination produced stronger effects than either drug alone, although this was observed in a limited number of measures. These data importantly provide the first empirical determination of the effects of the methamphetamine-oxycodone combination.


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More About This Work

Academic Units
Thesis Advisors
Hart, Carl
Ph.D., Columbia University
Published Here
July 7, 2014