In post-industrial societies, drug using conducts have increased exponentially in the last decades and virtually all psychoactive substances are now easily accessible via the Internet. Although drug use has been assimilated in mainstream lifestyles, and involves significant portions of the population, the legal status of drugs maintains the phenomenon submersed. In this work, which comprises of four major studies and two additional experiments, the issue is addressed by using both quantitative and qualitative methods to address methodological issues and provide insight regarding the novel developments of the phenomenon. Two experiments within an ecological setting using a known group of recreational cocaine users and a verified abstinent comparison group found strong evidence that questioned the validity of autobiographical Implicit Association Test (aIAT). In Chapter 2 Study 1 (n=46), the cocaine and heroin aIATs identified 61% drug users in the abstinent control group. The aIAT outcomes are heavily influenced by social knowledge and currently the test cannot be used to assess an individual’s drug using status. Results from Study 2 (n=41) and Study 4 (n=31) make a significant contribution to the understanding of the aIAT mechanism by highlighting its malleability to stimuli framing and instructions. The high accuracy (97%) of the gender aIAT (Study 3, n= 41) reassures that the aIAT is accurate when the target concept (i.e., gender identification) is deeply engrained. Chapters 3 and 4 used mixed methodologies (IATs, questionnaires, vignettes and interviews) to explore the social-psychological aspects related to the misuse of prescription psychostimulants. In Chapter 3, it was found that university students (n=98) hold functional views towards chemical enhancement. In Chapter 4 through qualitative interviews (n=13), it was confirmed that prescription psychostimulant abuse is a novel trend reflecting a generalized tendency to view drugs as instrumental for the adaptation to contemporary social contexts. These attitudes are partially forged by previous experiences with other mind-altering substances. Outcomes of this work suggest that employing mixed methodologies is advisable in substance use research and that progressive public policies should move away from viewing drug use as deviance and confront the issue acknowledging its consolidated presence in post-industrial societies.