The information on this study is limited as it looks at usage over a 30 day period when physiological changes can take years to fully manifest. Long term consistent use of cannabis (and its derivatives) during adolescence can cause many problems ranging from decreased gray matter up to mental instability (problems controlling anger, memory issues, paranoia, depressive like symptoms)
Its too bad that however that you didn't read the full article as if you did you would have surely written about that as they bring it up.
I did read the research. The test sobjedt were people that use alcohol and cannabis for years, not 30 days.
Cannabis don't change your brain, in any similar way.
I use cannabis regularly, since I was 15, I'm 35 now.
I can tell you for sure, cannabis is good for you☺
I am going to respond to both of your replies by responding to this one.
The participants were deemed to have used cannabis as long as they used cannabis in the past 30 days meaning that this study doesn't look at how much is being used. The manipulated variable is just whether they used alcohol, marijuana, or both, oh and age groups.
Read my sources, you are correct in saying it doesn't change it in similar ways (as long as by similar you mean the same) but it does change it, for the worse. The final results are similar over chronic long term usage.
That is not surprising honestly...
Long term usage can cause many detrimental effects ranging from memory issues to behavioral issues. That is just on the brain, there were also studies looking at the damage caused by specific ways of intake finding that smoking it can lead to esophageal damage and has studies able to find that it can increase effectiveness of certain mutagens (i.e. increase risk of certain cancers in head or neck)
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I am just going to drop my reference here from before which cites multiple studies that have found changes in WM (white matter) and GM (gray matter) and this source was given in the first comment.
I conclude that marijuana usage after development has finished poses low risk in low to moderate usage but with chronic usage it can increase the risk of many things ranging form cognitive debilitation to a more physical change.
Also, the researchers tested the influence of grey and white brain matter, not the influence of their behaver.