Free online test shows if you have cannabis-induced brain damage

Hey folks. I’ve recently quit weed after 6+ years of moderate use. Reason is, I’m almost certain it’s caused me some minor brain damage. This definitely isn’t a “weed is dangerous” post – it’s purely to inform people about a lesser-known effect of cannabis.

In a nutshell, some areas of the brain see a reduction in gray matter from cannabis use, especially the orbitofrontal cortex. These areas involve decision making, social behavior and personality.

The test is called the Iowa Gambling Task (invented in 1994). If you plan to take the test, do it before you continue reading below, and don’t look at mine or anyone else’s results til afterwards, or your own results will be inaccurate. Back in the day they’d use paper cards, now there are many free online versions out there. It can only give you accurate results one time.


So here are my results. My decision making is clearly diminished, and I strongly suspect I have a big reduction in gray matter in my prefrontal cortex, specifically the orbitofrontal cortex, due to long-term smoking of 1g/day or more

Some quick brain anatomy: The prefrontal cortex (PFC) is involved in planning complex cognitive behavior, personality expression, decision making, and moderating social behaviour. The orbitofrontal cortex (OFC) – an area in the PFC – represents emotion and reward in decision making.

Long term cannabis use reduces grey matter in the PFC, and especially in the OFC. There’s plenty of evidence of this from MRI scans from cannabis users, as well as studies of executive function and reliable meta-analyses. The level of damage seems to depend mostly on your level of consumption in the previous 3 months, or how much you smoked in adolescence.

[In the Iowa Gambling Task] patients with orbitofrontal cortex (OFC) dysfunction, however, continue to persevere with the bad decks, sometimes even though they know that they are losing money overall.

That was me essentially. Other behaviors I was exhibiting:

  • Severe risk taking – e.g. I would jaywalk in dangerous circumstances, or gamble large amounts of money, and felt no fear at all.

  • Social life basically nil – I couldn’t get the basics right and wound up with almost no social life.

  • Reward systems were messed up, hitting goals gave me no pleasure. Massive procrastination, my degree took twice as long as it should have.

  • Depression, insomnia, weight gain – all symptoms of OFC damage as well.

Gonna see if quitting helps, and am getting an MRI just to see. If you recognise these behaviours in yourself, consider whether weed is the cause and whether it’s time to cut back or take a break.

Hope this has been informative. Post your results here, it’d be interesting to compare.

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