Did Vietnam Vets really experience a lot of substance abuse and have addictions as a result?

As others have noted elsewhere, there's no simple answer to yoijr question. Between 1965 and mid-'68, drug abuse was minimal because there were a large number of regullar army troops in the ranks. As the number of draftees increased and the amount of violent combat actions lessened, the amount of drug abuse climbed.

Marijuana was used the most, but people wanting harder stuff had little trouble finding it. Heroin in Vietnam had a reputation for being mucn stronger than that available in the states because of its purity.

By the time I arrived in the summer of 1970, pot smoking was virtually ubiquitous--especially in the rear areas. Grunts, for all intents and purposes, never used in the field. It didn't take a rocket scientist to figure out that someone smoking dope was a hazard to his fellow soldiers.

By 1971 they had developed a urine test that could ID heroin abusers and every soldier and Marine leaving the country had to pass a "piss test" before being cleared for departure.

This is really a hard question to answer as Vietnam was a long war and changed over time. My great-Uncle was there 70-71 and he said that the 'widespread' use of drugs etc, wasn't the reality. Then you get guys who definitely did drugs and had issues as I'm fairly sure everyone has seen the famous clip of a group of soldiers using a shotgun to do drugs.

If you're meaning coming home and having issues, then I'd have no doubt as we've seen the same play out in GWOT Veterans as well. Self-medication has always been a way in which Veterans deal with the stresses brought on by deployment.

The simple answer is yes! In my unit, 299 engineer btn. I personally witnessed lots of pot smoking. You could easily buy a pack of "cools" that was packed with weed, cleverly sealed to make it appear unopened, had a filter and all! I recall troops heading to guard duty and gulping down a bottle of "obesidol" a potent diet medicine, (speed), and at the end of their shift, popping "Binoctol" a downer to sleep. There were little road side pharmacies with all that stuff. Yes heroin played a big part too. A guy in my company was so strung out on "H" he kept extending his tour in Nam. You may be wondering about me? I hit a joint every now and then. I remember smoking a joint painted with opium tar. Sent me flying, literally! Never did hard drugs like "H" and stateside my beverage of choice is vodka, nothing else.