Self-medication is a human behavior in which an individual uses a substance or any exogenous influence to self-administer treatment for physical or psychological ailments. Self-medication is a human behavior in which an individual uses a substance or any exogenous influence to self-administer treatment for physical or psychological ailments. The most widely self-medicated substances are over-the-counter drugs used to treat common health issues at home, as well as dietary supplements. These do not require a doctor's prescription to obtain and, in some countries, are available in supermarkets and convenience stores. The psychology of self-medicating with psychoactive drugs is typically within the specific context of using recreational drugs, alcohol, comfort food, and other forms of behavior to alleviate symptoms of mental distress, stress and anxiety, including mental illnesses and/or psychological trauma, is particularly unique and can serve as a serious detriment to physical and mental health if motivated by addictive mechanisms. In postsecondary (university/college) students, the use of self-medicating of study-drugs such as Adderall, Ritalin, and Concerta has been widely reported and discussed in literature. Products are marketed by manufacturers as useful for self-medication, sometimes on the basis of questionable evidence. Claims that nicotine has medicinal value have been used to market cigarettes as self-administered medicines. These claims have been criticized as inaccurate by independent researchers. Unverified and unregulated third-party health claims are used to market dietary supplements. Self-medication is often seen as gaining personal independence from established medicine, and it can be seen as a human right, implicit in, or closely related to the right to refuse professional medical treatment. Self-medication can cause unintentional self-harm. Generally speaking, self-medication is defined as 'the use of drugs to treat self-diagnosed disorders or symptoms, or the intermittent or continued use of a prescribed drug for chronic or recurrent disease or symptoms' As different drugs have different effects, they may be used for different reasons. According to the self-medication hypothesis (SMH), the individuals' choice of a particular drug is not accidental or coincidental, but instead, a result of the individuals' psychological condition, as the drug of choice provides relief to the user specific to his or her condition. Specifically, addiction is hypothesized to function as a compensatory means to modulate effects and treat distressful psychological states, whereby individuals choose the drug that will most appropriately manage their specific type of psychiatric distress and help them achieve emotional stability. The self-medication hypothesis (SMH) originated in papers by Edward Khantzian, Mack and Schatzberg, David F. Duncan, and a response to Khantzian by Duncan. The SMH initially focused on heroin use, but a follow-up paper added cocaine. The SMH was later expanded to include alcohol, and finally all drugs of addiction. According to Khantzian's view of addiction, drug users compensate for deficient ego function by using a drug as an 'ego solvent', which acts on parts of the self that are cut off from consciousness by defense mechanisms. According to Khantzian, drug dependent individuals generally experience more psychiatric distress than non-drug dependent individuals, and the development of drug dependence involves the gradual incorporation of the drug effects and the need to sustain these effects into the defensive structure-building activity of the ego itself. The addict's choice of drug is a result of the interaction between the psychopharmacologic properties of the drug and the affective states from which the addict was seeking relief. The drug's effects substitute for defective or non-existent ego mechanisms of defense. The addict's drug of choice, therefore, is not random.