Yes, there are big differences between the two. For instance, if you described a postal worker on a murderous rampage as "going berserk," you'd likely be wrong: "going postal" is actually a classic example of running amok. OK, so what about those opiate-induced rampages we see in Vietnam flicks, in which doped-up soldiers run screaming into the jungle, engaging the enemy with little regard for their own safety? Definitely not running amok: that's some classic berserking right there. Let's break it down.
To get to the bottom of this one, we've got to go on an etymological carpet ride, all the way back to the probably ancient Malay word "mengamuk," meaning "to go mad with rage." But mengamuk was a peculiar form of going mad with rage that was -- at the time Western observers began to record such things in the 19th century, in any case -- native to Southeast Asia. Here's how it went down, according to the Britannica:
"A Malay will suddenly and apparently without reason rush into the street armed with a kris or other weapons, and slash and cut at everybody he meets till he is killed. These frenzies were formerly regarded as due to sudden insanity. It is now, however, certain that the typical amok is the result of circumstances, such as domestic jealousy or gambling losses, which render a Malay desperate and weary of his life. It is, in fact, the Malay equivalent of suicide. The act of running amuck is probably due to causes over which the culprit has some amount of control, as the custom has now died out in the British possessions in the peninsula, the offenders probably objecting to being caught and tried in cold blood."
There seems to be a direct link between such behavior -- the end result of which is usually the death of the amok-runner -- and massacres like Columbine and the murder-suicide rampages of postal workers. Which puts all this squarely in its own category, and distinctly apart from
Most closely associated with the Norse Berserkers, gangs of warriors who fought in an uncontrollable rage. The difference between their uncontrollable rage and that of Malay amok-runners is that the Berserkers -- prized by the Scandinavian kings who commanded them for their ferocity -- generally loosed their inner beasts only in battle, and directed it toward the enemy rather than indiscriminately. They are depicted in Icelandic sagas as wearing bear pelts on their heads ("berserker" loosely translates to "bear skin") and wielding throwing axes with deadly precision.
Yet many modern theories attribute their ferocity to the ingestion of everything from the psychoactive fly agaric mushroom to wolf's blood -- though how you throw an axe precisely while being hopped up on ancient goofballs is beyond me (and many experts). Another (hilarious) theory posits that the Berserkers were manic-depressives, and their deadly rages were actually manic episodes. (I have some manic friends, and none of them have thrown an axe at my head ... yet.)
Anyone got a better explanation -- or better yet, a deep indwelling of insatiable rage they'd like to share?