likely took other drugs at times
I'm from the exact same generation.
At least two of my high school classmates went to Yale with Kavanaugh (same class). I didn't hang around with the athletes in high school, but was aware they were up to much of the same as we were. The heavy drinking and music and trying to get girls. It was a mostly beer drinking culture, but we also had parties specifically with mixed-drink themes (my Alabama Slammer parties were legendary). It didn't take much to realize that girls drank more with mixed drinks, and was a fun change of pace.
I would be very surprised if Kav's buddies didn't have alcohol parties at times. I think one of the girls in or around his HS circle from back then mentioned Everclear, which is undiluted grain alcohol. Knowing what I do about the time and culture, I find it exceedingly unlikely that Kav and his friends didn't smoke weed. Which was exceedingly commonplace. And probably at least dabbled in other drugs. They were readily available, common and considered cool/edgy.
I guess its mildly plausible they stuck to drinking, but I think the vast majority of middle class suburban teenage heavy drinking buddies circa 1983 also engaged and experimented with other drugs.
It's too bad he wasn't asked about other drugs under oath, because that's certainly on various gov't forms he would have filled out in the past.
I wonder if Mark Judge's book talks about smoking dope or taking other drugs in high school, because it would then be very likely Bart O'Kav did as well.