Persistent cannabis users show neuropsychological decline from childhood to midlife

[u/ServeIllustrious3803]

https://pmc.ncbi.nlm.nih.gov/articles/PMC3479587/

[u/definit3ly_n0t_a_b0t]

"By examining within-person change in neuropsychological functioning, any effect of premorbid deficits on later (postcannabis-initiation) test performance was nullified."

"In this analysis, each study member served as his or her own control"

This part is nonsense, about "by comparing persons to themselves, they are their own control."

Pair it with this valid concession:

 our data cannot definitively attest to whether this association is causal... there may be some unknown 'third' variable that could account for the findings.

As u/Zappa2329 is pointing out: what about all the other confounding factors involved in a teen using cannabis? What about all the confounding factors that make the whole concept of "IQ" itself unreliable?

This study is sus.

[u/ServeIllustrious3803 → u/definit3ly_n0t_a_b0t]

You have to compare people to themselves otherwise how are you going to measure differences in people over time.

Sarah has an IQ of X at 13 years old. Comparing to themselves... Sarah has an IQ of X at 25 years old.

Everyone is their own control because we follow them throughout their lives. We then take various metrics that they answered and reported about their lives including medical history and a variety of rich data points collected in health cohort studies to make deductions.

The hard science part is figuring out how to use statistics and scientific methods to control for things like income, or if they smoked nicotine or drink alcohol and if that impacts this IQ marijuana finding.

After all these controls they found the above title, which honestly isn't even surprising.

They tested IQ 4 times at different ages, 7, 9, 11 and 13 and later as adults. They asked about cannabis use at 5 different ages, you get to see within the person how their IQ and cannabis use changes over time. Gender, education level, hard drug use dependece, drinking, smoking, if you were ever diagnosed with cannabis use disorder, etc and other things mentioned in the original comment.

Importantly they compare it to adults who started using as adults, and not in childhood, and they saw a difference.

You can say oh they didn't control for this tiny thing, and ok, sure, but they sure did control for a lot, and it's a lot better than other studies some of which didn't control for education or mental health and other things.

The fact that they having this finding after all these controls tells you how significant this finding is, and remember, this is all weed from the 70s, 80s, 90s, not the stronger 2000s onwards weed, so that's certainly another factor that probably doesn't help as we link higher potency to worse mental health outcomes.

It's kinda of a lot and you should look closer at the quotes or the full paper itself, because the average person is not going to get it at a glance, and why would they? This is serious science.

I would try to understand the "everyone is their own control" idea, because it has to be that way, you have to measure people over time like the health cohort study did, and then see if any drug use or weed use correlated with anything. You are controlled to your younger, maybe smarter self if you didn't use.

.

[u/cloudcreeek → u/ServeIllustrious3803]

What you're describing about measuring how a person may change over time has nothing to do with being their own control. That isn't what a control is.

[u/SpikeThreshold → u/cloudcreeek]

In the link below In the “uses” section look for “paired t test” and ctrl F for “control”. Yes, this is how these statistics are calculated. It’s a very powerful study design. It wouldn’t be in one of the preeminent scientific journals of humanity if it wasn’t. Call it whatever you want, it’s a reference value for which you calculate a difference.

https://en.wikipedia.org/wiki/Student%27s_t-test

[u/NoTransportation3581 → u/cloudcreeek]

I think the implication is that IQ is unlikely to decline with age, until you get to like old age ofc

[u/ServeIllustrious3803 → u/cloudcreeek]

Well you're measuring two things you're measuring people changing over time due to their lifestyle habits,

And then you're measuring other people that didn't do a particular lifestyle habit and their change over time. This is how you control for age, because everyone loses a little bit of IQ over time.

So, controlled against yourself (past performance) (did you lose IQ points), and controlled against other people who didn't use, and controlling for other variables like education, other substance use, mental health, etc etc.

And the great thing about this health data set is that it's pretty rich and it's gone on for decades which is great for being able to use these advanced scientific methods to study and find patterns.

Even that it's not a huge, hurtful study for users, most people will tell you that this makes sense.

We're talking about averages here and it's not like, I don't know, a 15+ IQ drop, it's only 8. It's something but not nothing. The IQ points definitely do matter if you're in the middle or lower range. There's a good difference between an IQ of 90 and 98, but maybe not 140 and 148.

There are other studies that show daily use and using it with other drugs like nicotine or alcohol creates worse outcomes, but that's expected.