Key Concepts

 

1. Substance Use Disorder (SUD)

According to the DSM-5, a substance use disorder is a compulsive pattern of drug use despite negative consequences. People with SUD often:

• Use more of a drug than intended.
• Continue using despite social, health, or legal problems.
• Experience difficulty controlling their use.

2. Physical Dependence vs. Psychological Dependence

• Physical dependence: The body adapts to a drug, leading to withdrawal symptoms when use stops.
• Psychological dependence: An emotional or mental craving for the drug.

3. Tolerance and Withdrawal

• Tolerance occurs when increasing amounts of a drug are needed to achieve the same effect.
• Withdrawal refers to unpleasant symptoms that occur when drug use is reduced or stopped. These symptoms are often opposite to the drug's effects.

Major Drug Categories

Drug Category	Examples	Primary Effects
Depressants	Alcohol, barbiturates, benzodiazepines	Slow nervous system activity; often affect GABA neurotransmission
Stimulants	Cocaine, amphetamines, MDMA, cathinones	Increase alertness, energy, and dopamine activity
Nicotine & Caffeine	Tobacco products, coffee	Affect acetylcholine and adenosine systems, respectively
Opioids (Opiates)	Morphine, heroin, codeine	Powerful pain relief; act on endogenous opioid systems
Hallucinogens	LSD and others	Alter perception, sensory experiences, and consciousness

Main Takeaway

All psychoactive drugs alter consciousness by interacting with the brain's neurotransmitter systems. While some drugs have medical uses, misuse can lead to tolerance, dependence, withdrawal, and substance use disorders. The DSM-5 emphasizes that the defining feature of a substance use disorder is continued use despite significant negative consequences, not simply physical dependence alone.