Hacker News Reader

This seems to be a simple correlational study with the added bonus that abnormal hippocampi is also correlated with pot usage.

There isn't even an attempt to establish any sort of causality here yet the article uses the word 'affects'.

View on HN

“It is possible that the abnormal brain structures reveal a pre-existing vulnerability to marijuana abuse,” Smith said. “But evidence that the longer the participants were abusing marijuana, the greater the differences in hippocampus shape suggests marijuana may be the cause.”

Correlation, sure, but correlation with length of usage. Definitely a more interesting angle than simply usage <-> deformation.

It's a bit difficult ethically to assign one group of teenagers to the marijuana group and one to the clean group...

Reply on news.ycombinator.com