We devised a set of survey questions to measure happiness. Although an abstract quality, ones happiness index can be boiled down to several circumstantial evidences. The survey also included questions regarding the volunteer's drug use habits and reasons. After collecting the results, we found a direct positive correlation between the happiness index and drug use. The following research was done to find a cause behind this relationship. We targeted specific brain neurotransmitters because they are responsible for mood regulation and also heavily effected by drug use. The study concerns three neurotransmitters, gamma-amino butyric acid, serotonin and dopamine. These are some of the most important mood regulatory neurotransmitters. The study analyses the effects of the three most commonly recorded drugs in our survey: nicotine, cannabis and alcohol respectively. Each drug negatively affects the particular neurotransmitter in a different way thus affecting its functions, which have a direct influence on depression.