This summary, written by Yosef Bronsteyn, is based on an article by Murray, Li, Weafer and de Wit (2021): Subjective response predicts d-amphetamine choice. Pharmacology, Biochemistry and Behavior, 204 (2021) 17358.
Is it their personality? To “escape” a negative mood? Social pressure? The desire for pleasure? A combination of factors?
Many previous studies reviewed by this laboratory found that experiencing pleasure or euphoria after using stimulants like d-amphetamine predicts future usage.
Many previous studies reviewed by this laboratory found that experiencing pleasure or euphoria after using stimulants like d-amphetamine predicts future usage. But stimulants can also induce negative feelings. According to previous research by this laboratory, the anxiety or depression induced in some individuals who use amphetamine predicts subsequent non-usage. However, the nausea induced by nicotine in first time users has been shown to predict subsequent usage. Furthermore, a 1991 study suggests that Opiate usage continues even in the absence of euphoria.
Previous but contradictory research found that a person’s mood prior to using amphetamine effects future usage. One study found a negative baseline mood predicts amphetamine choice; another found it was a positive baseline mood and others found that prior mood made no difference. Another variable that could affect drug usage is personality, but despite a link to subjective drug response, it does not robustly predict usage according to prior research.
Murray et al attempts to expand upon prior findings. Importantly, a higher dose of d-amphetamine (20mg) was used than previous studies because this dose has been shown to reliably induce euphoria. Across 2 visits, 112 volunteers were administered 20mg of d-amphetamine per visit and placebo pills on 2 additional visits. Prior to these visits, volunteers completed a personality assessment. During these visits, volunteers were asked about their current mood, subjective states (e.g. energy levels) and their heart rate and blood pressure was measured; these measures were administered prior to taking the pills and every 30 minutes thereafter. Importantly, pills were color coded and participants were not told which colored pill was the d-amphetamine and which was the placebo, although they were told that pills were one of the two. On a fifth “choice session” participants reported their response to both pills during the previous 4 visits—specifically, whether they “felt” an effect, whether they “liked” the feeling and whether they would “pay” for each pill. Participants were then asked to choose to take one of the colored pills. Eighty-one participants chose d-amphetamine and 31 chose the placebo pills.
This study found that the “Choosers” reported higher increases in positive mood, elation, energy, wellbeing and intellectual productivity after taking d-amphetamine than did the “Non-Choosers.” Choosers more accurately guessed that the colored pill containing d-amphetamine was in fact a stimulant as compared to the Non-Choosers. Both groups experienced similar increases in heart rate and blood pressure after taking d-amphetamine. Crucially, despite having both felt the effects of d-amphetamine, the Choosers liked those feelings more and were more willing to pay for the drug. Among the Choosers, the average dosage chosen was 3 and ½ pills, supporting prior findings that 20mg (4 pills) is around the dosage that reliably induces euphoria. This study did not find personality, mood, or heightened post-drug anxiety to effect d-amphetamine choice. Only the subjective “liking” of d-amphetamine predicted subsequent usage. This study was conducted within a supervised laboratory setting and only with mentally and physically healthy volunteers. More work is needed that examines the reasons why individuals in the “real-world” choose to take d-amphetamine. Real world settings include a more diverse range of individuals and factors such as social pressure that could contribute to d-amphetamine choice.
Read the whole study here.