From the article: "On average, the marijuana users who participated in the study consumed the drug three times per day." ^ Of course there's a brain decline if

From the article: "On average, the marijuana users who participated in the study consumed the drug three times per day." ^ Of course there's a brain decline if you smoke it 3 times a day. That's being perpetually high. If you drink alcohol heavily 3 times a day you'll also decline pretty rapidly.