Numerous studies have conclusively shown that almost any man or woman has the potential to become addicted to almost any substance, activity or object. The rate at which men and women are susceptible to various addictions may be affected by the hormonal, physiological, and psychological differences found between men and women. While addiction does not pick and choose its victims, the susceptibility of men and women to any number of addictions to various substances and activities does indeed vary depending on gender. Studies demonstrate that there are various male and female risk factors associated with different habit-forming addictions. These studies show that males and females are different in their motives to use drugs or other substances, their vulnerability to addiction, and also in their physical and mental reactions to the various addiction treatment therapies. The key substance that is responsible for these differences is the release of dopamine in the brain and how the gender determining sex hormones of testosterone and estrogen affect its release. Dopamine really is the prime substance that underlies the changes that occur in the rewards and pleasure centers of the brain that happen as a result of addiction. The release of dopamine is why humans continue to repeat behaviors that cause its release, and why humans find activities such as eating and having sex as pleasurable and relaxing. Dopamine release is thought to have been an adaptation that ensured the survival of early humans by encouraging them to participate in activities that increased their chances of survival. Dopamine release plays a part not only in the development and reinforcement of many addictions, but is also a signature chemical in other physical and mental illnesses. This may help to explain why those who suffer from mental illnesses seem to self-medicate and have a higher tendency for various addictions. The sensations that we experience as the result of having sex or eating, also occurs in many types of addiction, as even thinking about obtaining the addictive substance or habit can cause the release of dopamine in the brain. While both males and females produce dopamine, the way that this substance interacts within the brain varies greatly due to the production and effects of various hormones that are also released in the bodies of males and females. Two hormones that are responsible for many of the characteristics of gender, estrogen and testosterone, both affect the levels of dopamine released and how it is released. Because of this link between hormones and the fact that the amount that is produced by each of these hormones is determined by one’s gender reinforces the link between addiction and dopamine release and demonstrated the difference between the sexes as to how and why they use drugs. A prime example of this is cocaine. Studies reveal that women tend to use cocaine to self-medicate when feeling depressed and unhappy, when their levels of estrogen are fluctuating rather than being like men, who typically use cocaine when they are feeling good, in order to feel even better. Happiness in men has been linked to an increase in circulating testosterone levels. Both hormone release and how they affect the release of dopamine then affect the way addiction to cocaine plays out in men and women. Nicotine addiction is also affected by gender. Studies show that women use smoking to regulate their mood and suppress their appetite, while men generally smoke to improve their attention and performance at work and also to relieve feelings of anger or sensations of pain. The hormones of estrogen and testosterone and how they affect the release of dopamine play a large part for the differences in susceptibility to addiction in men and women who consume tobacco products. The susceptibility for alcohol abuse is yet another area where men and women differ, as women begin drinking to compensate for feelings of emptiness or loneliness and men tend to use alcohol like cocaine in that it is used to either relax or to celebrate sensations of happiness or to increase feelings of confidence. Nearly all substances and activities are now showing a clear link between dopamine release and how male and female hormones affect the progress and treatment of the addiction.