Psychoactive drugs alter mood and perception by interfering with neurotransmission. There are four main categories of psychoactive drugs: depressants like alcohol which reduce neural activity; opiates like morphine which reduce pain and induce euphoria; stimulants like cocaine which excite neural activity; and hallucinogens like LSD which distort sensory perceptions. Long term use of psychoactive drugs often leads to tolerance, physical dependence, and withdrawal symptoms due to changes in the brain's neurochemistry.

1. Psychoactive Drugs

2. Psychoactivity and Dependence

8. Tolerance

10. Why do people abuse drugs? Biopsychosocial Theory

11. Drugs and Neurotransmission

15. Neural Activity

16. Neurotransmitters and the Synapse

18. Reuptake

21. Drug Classifications

23. Drug Classifications: Depressants

29. What do we mean by “one drink?” One 12-ounce can of beer has about the same amount of alcohol as 4 ounces of wine or 1 ounce of whiskey

32. Alcohol’s Affect on the Brain Alcoholism shrinks the brain

40. Drug Classifications: Opiates

45. Drug Classifications: Stimulants

50. How Cocaine Works

52. Drug Classifications: Hallucinogens

61. Prevention