psychiatric disorders
Overview of Substance Use
Introduction
Substance-related disorders involve substances that directly activate the brain's reward system. The activation of the reward system typically causes feelings of pleasure; the specific characteristics of the pleasurable feelings evoked vary widely depending on the drug. These drugs are divided into 10 different classes that have different, although not completely distinct, pharmacologic mechanisms. The classes of drugs include Alcohol Use Disorder and Rehabilitation None Caffeine Marijuana (Cannabis) and Hallucinogens (eg, LSD, Volatile Solvents (volatile hydrocarbons [eg, paint thinner, certain glues]) Opioid Use Disorder and Rehabilitation (eg, Sedatives (eg, Stimulants (eg, Amphetamines , Smoking and Other Tobacco Use None Other (eg, Anabolic Steroids ) This classification is not based on whether a drug is legal (eg, alcohol,caffeine), illegal (eg, hallucinogens), or available by prescription (eg,morphine,lorazepam). Specific details regarding these drugs and their effects are discussed elsewhere in THE MANUAL. The term "narcotic" is a legal and colloquial term. Originally, it referred to drugs that caused narcosis (insensibility or stupor), particularly opioid drugs (eg, opium, opium derivatives). However, the term is currently used so inconsistently (eg, the US government classifies the stimulant drugcocaineas a narcotic) that the term has little scientific or medical meaning. Use and cessation of substances may cause psychologic, behavioral, and physiologic changes, ie, intoxication and withdrawal. Substance misuse can also result in psychiatric disorders (eg, Depressive Disorders , Substance use disordersinvolve a pathologic pattern of behaviors in which patients continue to use a substance despite experiencing significant problems related to its use. There may also be physiologic manifestations, including changes in brain circuitry. The common terms "addiction," "abuse," and "dependence" are too loosely and variably defined to be very useful in systematic diagnosis; "substance use disorder" is more comprehensive and has fewer negative connotations. Drugs in the 10 classes vary in how likely they are to cause a substance use disorder. The likelihood is termedaddiction liabilityand depends upon a combination of factors including Route of administration Rate at which the drug crosses the blood-brain barrier and stimulates the reward pathway Time to onset of effect Ability to induce tolerance and/or withdrawal symptoms 