All the major biological explanations related to drug abuse assume that these substances exert their ________ effects by altering brain chemistry or neuronal activity.

• A. Psychotic
• B. Psychoactive
• C. Physiological
• D. Central nervous system

Answer: (B)

The main idea is that drugs are described by the kind of mental effects they produce, which come from changes in brain chemistry and neuronal activity. The term that fits this description is psychoactive—it means substances that act on the brain to affect thoughts, mood, and behavior. All major biological explanations of drug abuse assume these substances have psychoactive effects by altering neurotransmitter systems and neural circuits. The other options don’t capture this focus: psychotic describes a clinical state involving loss of reality, not a general property of drugs; physiological is too broad and not specific to mental or behavioral effects; central nervous system refers to where the effects happen, not the nature of the effects themselves.