Researchers led in part by Ryan McLaughlin at Washington State University published a study in Neuropsychopharmacology examining why some rats seek cannabis. They built a behavioural profile for each rat, testing social behaviour, sex, cognition, reward and arousal. Over three weeks, rats were observed for one hour daily in an airtight chamber where a nose-poke released three seconds of cannabis vapor; students counted each nose-poke.
The study found a clear correlation between nose-poke rates and baseline corticosterone, the rodent equivalent of human cortisol. It was resting baseline stress, not short-term stress after a challenge, that related to self-administration. The researchers also linked stronger cannabis-seeking to reduced cognitive flexibility and greater reliance on visual cues.
They identified a weaker association when high morning corticosterone occurred with low endocannabinoid levels. Endocannabinoids are compounds produced on demand to help maintain physiological balance. McLaughlin suggested THC might sometimes substitute for lower endocannabinoid tone. The team said these findings could point to early markers for screening and prevention, and that baseline cortisol assessment might one day give insight into later problematic drug use patterns.
Difficult words
- behavioural — relating to actions or observable reactions
- corticosterone — a stress-related hormone in rodents
- baseline — a normal starting level for comparison
- self-administration — voluntary use or intake of a substance
- cognitive flexibility — ability to change thinking or strategies
- endocannabinoid — naturally produced compounds that affect body balanceEndocannabinoids
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Discussion questions
- How could measuring baseline cortisol or corticosterone help prevent later problematic drug use? Give possible benefits and limits.
- What ethical or practical issues arise when using rat behaviour to predict human drug use?
- The researchers mention endocannabinoid levels. How might knowing someone's biological markers affect early screening or treatment choices?
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