What does cross-tolerance refer to, and how can it affect overdose risk in poly-substance users?

• A. Tolerance to one depressant increases tolerance to another; risk of overdose when switching substances or combining.
• B. Tolerance to one depressant decreases tolerance to another.
• C. Tolerance to one depressant has no effect on tolerance to other drugs.
• D. Cross-tolerance only applies to stimulants.

Answer: (A)

Cross-tolerance happens when tolerance to one depressant makes you less sensitive to another depressant that acts on similar brain pathways. Because these drugs often enhance the same inhibitory signals in the brain, your body becomes accustomed to their effects, so you may need more of the second drug to feel it. In real life, a person switching from one depressant to another or using both can misjudge how much they’ve taken and end up overdosing, since the combined or substituted drug can have stronger depressant effects than expected. This explains why tolerance to one depressant can transfer to another and why overdose risk rises with switching or poly-substance use. It’s not about decreased tolerance, it isn’t limited to stimulants, and it can occur among various CNS depressants with shared mechanisms.