Three groups will be tested on their level of subjective well-being (SWB), personality characteristics, self-esteem, optimism, and perceived control. There will be, a control group of non-drug users, one group comprising individuals who have been on the methadone program for less than one year (ST), and the other group comprising individuals who have been on the methadone program for more than one year (LT). Essentially, the ST group will be expected to have lower levels of SWB, self-esteem, optimism and control. They are not expected to have adapted to their treatment regime yet, and as such the restricted freedom and control would defeat the homeostatic mechanism regulating SWB, thus reducing the individual's level of SWB. The LT group, are expected to have adapted to their circumstances, and be benefiting from the methadone. Therefore, their levels of SWB should be returning to the set-point range. However, in comparison to non-users, heroin users are reported to be more neurotic. Neuroticism is responsible for delivering negative affect to the system. Subsequently, their set-point range, and resulting level of SWB is expected to be lower than the controls.