The modern medical science has yet to figure out all of the organic causes of depression. Interestingly, the brain receptors that traditional drug makers have persistently disregarded so far, have become the golden mine for the illicit drug industry.
It is a known fact that some people are completely indifferent to pain pills, while others become addicted after taking only a few Vicodin after a dental surgery. The answer to these varying degree of susceptibility may be hiding in the emerging theory of Endorophine System Deficiency. Opioids are substances that stimulate the same receptors as endorphins that are produced in our body naturally. Some people are born with lower than normal levels of these endorphins than others and spend their lives feeling for the most part unhappy and miserable deep inside. Until one day, when they discover opioid narcotics and begin to self medicate their depression.
Unfortunately, their initial bliss is short lived. The majority of narcotic pain meds are not suitable for long term use as tolerance and dependence develops very quickly, requiring higher and higher doses to achieve the desired effect. The way these drugs were designed and the euphoria they tend to induce makes them very prone to abuse. In fact, quite the opposite- the depression is likely to worsen during the periods of abstinence.
2. Endocannabinoids. Another system that definitely plays role in our mood is endocannabinoid system. A few years ago, Sanofi-Aventis released an anti-obesity drug called Rimonabant on the European market. The drug worked by blocking the cannabinoid receptors of the brain, -the effect exactly opposite to the one exerted by marijuana which stimulates them. The idea was based on the logical conclusion that since cannabis are known to stimulate appetite in most people, the drug with the opposite action on the same receptors will lead to reduced appetite and weight loss. The theory proved it be correct: Rimonabant worked but its time under the sun was cut short as it was withdrawn from the market just a few years later. The reason it was pulled off was due to the reports of the serious side effects, namely severe depression and suicide in people who took it. This confirms that endocannabinoid receptors play a crucial role in our mood. READ MORE ABOUT DEPRESSION