The off-prescription use of modafinil and methylphenidate: Perceived risks, benefits and impact on cognitive function

Many psychoactive pharmaceuticals, in addition to their intended clinical benefits, can also enhance cognitive functions in healthy populations. Popularity in cognitive enhancing drug (CED) use has raised concerns about its possible risks and harms. Modafinil and methylphenidate are, perhaps, the most consumed CEDs. This thesis sought to understand more about the modafinil and methylphenidate off-prescription user and whether they are self-medicating for poor cognitive performance or enhancing. Study 1, an online survey advertised on forum sites to reach the CED-using and student populations, revealed that CED users are mostly male, North American or British, educated, employed and in their mid-20s. Use of CEDs was associated with recreational drug use and psychiatric disorders. Daily use of modafinil was reported as providing the most benefits and that benefits increased with more frequent use. Modafinil was perceived as safe, whereas methylphenidate was perceived as more dangerous. Study 1 could not assess whether CED-using respondents were self-medicating or enhancing, therefore, Study 2, an online survey, addressed this via the Cognitive Failures Questionnaire (Broadbent, Cooper, Fitzgerald & Parks, 1982), the General Procrastination Questionnaire (Lay, 1986), and the Adult ADHD Self-Report Scale, in addition to questions on CED and recreational drug use. The results revealed that the CED-user groups reported having problems with inattention and procrastination compared with controls. Study 3, an experimental study, sought to verify this objectively. The cognitive performance of 43 reported off-prescription users of modafinil and methylphenidate and 47 controls was tested using the Arrow Flanker Task (Ridderinkhof, van der Molen, Band & Bashore, 1997) and the Antisaccade task (Hallett, 1978), together with the self-report Behaviour Rating Inventory of Executive Function - Adults questionnaire (Gioia, Isquith, Guy & Kenworthy, 2000). The results indicated that the CED-user group demonstrated good cognitive performance and therefore were likely to be enhancing rather than self-medicating. The implications of these findings are discussed in relation to future research, ethical debates, and government policy.