Research conducted by Irwin, Bjurstrom and Olmstead (2016) aimed to study the relationship between sleep and cocaine and alcohol use.8 In this study, the participants were individuals who has previously been dependent on these substances but were now in the early stages of abstinence (Irwin et al., 2016). Polysomnographic sleep measures were recorded to determine sleep continuity, Stage 3 sleep and rapid eye movement (REM) sleep (Irwin et al., 2016). In this study, sleep continuity included the total sleep time, sleep latency, which is the time required to transition from full wakefulness to sleep, sleep efficiency and wake sleep onset (Irwin et al., 2016). Moreover, Stage 3 sleep was characterized by slow wave sleep (SWS), which consists of very slow delta waves in combination with smaller, faster waves in the brain (Irwin et al., 2016). These measurements were then compared to the controls, which were patients that had no medical history of any mental illnesses or disorders (Irwin et al., 2016). Although the results of the study indicated sleep continuity is not impacted by drug or alcohol use, the study did show that there was a decrease in Stage 3 sleep among both alcohol and cocaine-dependent patients (Irwin et al., 2016). The results also indicate that loss of Stage 3 sleep occurs at an earlier age among the cocaine-dependent patients, in comparison to the alcohol-dependent patients (Irwin et al., 2016). In addition, the amount of REM sleep increased among both groups of participants in comparison to the controls (Irwin et al., 2016). Therefore, this study demonstrates that alcohol and cocaine have an impact on sleep disturbances.