..Potpourri

Marijuana's been on people's minds for a long time -- about as long as it's been in people's minds. Consider:

More than 4,700 years ago, Chinese emperor Shen-Nung listed it in the first guide to herbal medicine, declaring it a useful treatment for everything from "female weakness [to] absent-mindedness."

A thousand years ago, a legendary Middle-Eastern cult that specialized in political murder was paid in a form of the drug called hashish. Their name, hashishiyya, still echoes in the English word "assassin."

In 19th Century France, a group of artists and poets turned on to pot and tuned into their experiences as a source of imagery and ideas. Their monthly gatherings formed the basis of the book, The Club of the Hashishins.

But if marijuana made a splash in centuries past, it was nothing like the tidal wave of interest it's kicked up lately.

Today, marijuana is the most widely-used illicit drug in the United States -- and in much of the rest of the world. In fact, according to a 2008 survey, more than 102 million Americans have tried pot, and about 16.5 million are regular users.

That's why  we've put together this pamphlet. Because marijuana's been poked and prodded, scrutinized and analyzed more than any other drug in history.

What that's meant is a much more complete -- and realistic -- picture of the full range of pot's effects than we've ever had before.

We hope you'll stick around to consider some of the more important ones.

Because marijuana is a complex drug, and it can cause a lot of subtle (and not-so-subtle) changes in the way we think and feel. And those changes are certainly worth thinking about if you're thinking about marijuana.

..How does pot affect personality?

In a lot of ways. But fully understanding all the ways it affects personality is like getting toothpaste back into the tube: tricky, at best.

One reason pot is hard to pin down is that it causes so many changes. In fact, researchers now think of the marijuana high as a group of overlapping effects involving different reactions in different body systems.

Still, what all the systems react to is a chemical called tetrahydrocannabinol, or THC, which triggers most of the mood and mind changes associated with pot.

Much of our understanding of how marijuana works is still sketchy, but it took a huge leap forward with the 1992 discovery of receptors for THC in the brain, docking sites for body chemicals much like THC.

Still, THC isn't the only chemical that swings into action when pot does its stuff. That's because marijuana isn't a single molecule at all (like alcohol or cocaine), but at least 400 different compounds -- 60 of which, known as cannabinoids, exist nowhere else in nature.

What THC and the other cannabinoids do is temporarily tilt the balance of chemicals in the brain involved in thought, feeling, and memory. Most effects -- from changes in perception to feelings of relaxation and euphoria -- usually peak within an hour and disappear altogether in 3-4 hours. Other effects may last longer.

..What other effects are there?

All kinds of effects. But the most important revolve around several key systems:

• Coordination. Even low doses can slow responses, making some tasks difficult, and others-driving, for example-potentially dangerous.
• Perception. Pot subtly alters sensory perception. Effects can include feelings of heightened sensitivity and a distorted sense of the passage of time.
• Mental Changes. Marijuana can impair judgment and reasoning skills, particularly those involved in counting and the ability to follow complex instructions. It also temporarily disrupts short-term memory.

..Does that mean pot smokers develop amnesia or something?

Not in the sense of forgetting their own name -- although they might have a problem with yours, if you were just introduced.

That's because THC loves to tinker with short-term memory. Even occasional use can cause problems, although it's more noticeable in heavy users.

Memory impairment shows up often in tasks requiring sustained concentration, but it turns up elsewhere, too. Communication is affected: speech slows, phrases get shorter, and users can forget what they're talking about--even in the middle of a sentence.

And even though performance and memory problems usually disappear as drug effects fade, long-term learning problems still haven't been ruled out.

..Are there other long-term risks?

Maybe. Because not all of pot's effects necessarily disappear when the high subsides. Subtle changes may continue.

In fact, one recent study showed that pilots' flying skills were still impaired 24 hours after smoking, even though the pilots themselves felt they were completely back to normal.

And since THC breakdown products, or metabolites, can linger in the body for days or weeks after use, this could be risky -- particularly for those involved in hazardous activities or occupations.

..Is pot stronger now than it used to be?

Yes and no. And maybe, definitely.

Government officials (especially those who get the biggest headlines -- and budgetary bumps -- from escalations in the "War on Drugs") claim that pot potency is up as much as ten times above levels of the 1970's.

Critics say such claims are based on hype, not history. They cite figures from the federal government's own analysis of 20,000 samples of confiscated pot tested over the past 20 years.

Test results show little evidence of surging marijuana potency -- except in the popular imagination and the media. In fact, tests reveal average pot potency in the United States to be fairly flat over the entire 20-year period, averaging 2.9 percent THC.

Still, even if people occasionally bend the truth, that doesn't mean the world isn't curved.

There is plenty of high-potency pot out there -- and it causes plenty of problems for some users.

..Does pot cause psychological problems?

That's another question that's hard to answer conclusively -- or quickly. But most authorities agree that pot can contribute to problems in susceptible people.

The most serious risk that a typical user ever runs is anxiety, which can be triggered by stress or fatigue-or higher-potency marijuana. Such reactions tend to be more common among infrequent and inexperienced users.

Pot-related panic typically lasts less than an hour, and generally requires little more than time to run its course, along with a little reassurance and TLC (not to be confused with THC) from friends or helpers.

Longer-term problems are more complicated and less-easily dismissed. Particularly troubling is a 1990 Swedish study, suggesting a link between pot use and schizophrenia.

In that study, researchers found that those who had smoked pot 10 times were 2.3 times as likely to be diagnosed with the disease as nonusers, while those smoking at least 50 times were 2.9 times more likely.

Cause and effect? Not necessarily, but it is worth thinking about -- and worth additional study.

..Pot Shots

Throughout history, no other drug has attracted more heat or inspired more heated rhetoric than marijuana. That's as true today as it's ever been.

And while we still haven't mastered all the mysteries of marijuana, we're closer to understanding it than we've been before.

We know it's a complex drug that triggers complicated changes in the body and brain.

We also know it can cause a range of reactions -- both pleasure and panic and possible longer-lasting changes, depending on dose and frequency of use.

And we know that pot poses potentially-serious risks to children, pregnant women, and those with underlying emotional problems.

And while we still don't know all we'd like about the effects of occasional use, we do know that people who smoke a lot of pot can have a lot of problems.

Don't be one of them.

Because problems -- whether they're caused by pot or not -- can be a lot easier to prevent than they are to predict.

..Sidebar 1 | Pot & Performance

Of all the charges leveled against marijuana over the years, one that's stuck longest--and has been most difficult to prove scientifically -- is its supposed link to "amotivational syndrome."

Symptoms of amotivation -- which include confusion, declining performance, and difficulty in finishing tasks -- are common enough among heavy smokers.

For now, though, marijuana and amotivation remains a chicken-and-egg question. Still unknown (and perhaps unknowable) is whether pot causes amotivation, or whether disaffected people smoke pot as a symptom of their alienation.

Similarly, changes that are sometimes blamed on pot use by young people--including changes in appearance and an increased desire for privacy -- are often only "symptoms" of growing up.

..Sidebar 2 | Smoke Signals

In most ways, marijuana ranks pretty low on the drug-problem totem pole. One reason: Pot's low toxicity. People don't overdose or lose their lives from smoking pot -- or at least not so anyone notices all at once.

Still, that doesn't mean people don't have problems with marijuana. They do.

But unlike other drug problems, signs of pot-related trouble may take a while to show up. And even when they do appear, pot problems can look more like good things that didn't happen in our lives than bad things that did.

How do you keep problems from happening to you? Here are a couple of ways:

• Don't smoke pot. That's the easiest way to avoid the issue. There's never been a documented case of anything disastrous happening to someone suffering from acute (or chronic) marijuana deficiency.
• If you smoke a lot, cut down. People who smoke a lot are more likely to suffer serious problems than occasional smokers.

And if not smoking for a day or two makes you feel tense, tired, anxious, or depressed, you might want to reconsider how much of your life you're devoting to the garden of grass inside your mind. Chances are you'll want to cultivate some new habits. Or weed out some old ones.