Smoking marijuana, the federal government constantly reminds us, is dangerous in every way. It impairs cognitive functioning, makes you high, and, because it's smoked, is a demon in a bong hit – and so on.

A counterargument is that pot has helped thousands of cancer and AIDS patients, for example, contend with side effects of their illnesses and treatments. There is also evidence that marijuana works for some psychiatric disorders as well, principally depression and bipolar disorder. Among some people, pot is jokingly referred to as "green Prozac."

The problem is you can't legally take a toke for psychiatric diagnoses.

"I think cannabis has a lot of potential in the treatment of mental illness," says Lester Grinspoon, emeritus professor of psychiatry at the Harvard School of Medicine. He says that it can be an effective treatment for bipolar disorder and depression. Like any medicine, he cautions, it won't work for everyone. Grinspoon has, over the last three decades, been one of the few psychiatrists willing to speak publicly on mental marijuana.

Most of the evidence to support use of pot as medicine is anecdotal; i.e., it seems to help AIDS and cancer patients contend with their diseases and handle the nausea they often experience from treatment, so there must be something to it. Many people also report that it provides a quick lift from the bowels of depression.

My own anecdotal, ahem, experience is that pot does indeed boost my mood from the badlands of depression and lower me from the Mount Everests of mania. I have no idea why or how, nor do I especially care – I'm one of those people who find Prozac and its progeny to be barely effective and with enough nasty side effects to outweigh the benefits. But I'll never tell that to the Drug Enforcement Administration or drug czar John Walters.

Instead, I'll let the Israeli army speak for me. Two weeks ago, it announced that it would provide, on an experimental basis, medical marijuana to troops suffering from post-traumatic stress disorder, another mental illness. Good enough for an army, good enough for me.

But in states with medical marijuana laws, each attempt to get depression or bipolar disorder added to the list of ailments for which the kine can be oh-so-kind has been shot down.

For example, four years ago, the Washington Medical Quality Assurance Commission was petitioned to add mental illness to its list of approved uses of medical marijuana. The commission denied the request. It argued that there was no lock-solid scientific evidence that weed worked for mental illness. The odd thing is that it had approved pot for treatment of Alzheimer's, Krohn's disease, chronic pain, and wasting syndrome based upon – you guessed it – anecdotal evidence.

The feds would like to keep any evidence that reefer is an Rx anecdotal – no peer-reviewed, double-blind studies here – as it bolsters their case that there's no scientific proof that pot works for anything except getting people high. It's the evil weed.

As proof, the DEA touts the following from a 1999 scientific report: It states that " . . . there is little future in smoked marijuana as a medically approved medication."

The report was prepared by the Institute of Medicine (IOM), part of the independent National Academies of Science. Interestingly, the feds lifted that quote from deep in the report. But perhaps more telling is that only one sentence later, the report says: "The personal medical use of smoked marijuana – regardless of whether or not it is approved – to treat certain symptoms is reason enough to advocate clinical trials to assess the degree to which the symptoms or course of diseases are affected."

The IOM backed that up with several strong recommendations that medical marijuana should be thoroughly studied – you know, like scientists study every other treatment under the sun.

To date, that hasn't happened.

"Who is going to get approval from an institutional review board to break the law?" asks Grinspoon. Researchers must have their studies cleared by such boards before they can do experiments with humans. He likens the situation to that of lithium. Its efficacy for treating mental illness was found by accident in the 1940s by an Australian scientist. The evidence was anecdotal. It wasn't until the late 1950s that the feds allowed it to be used in this country, despite the fact that it was saving lives on the other side of the globe.

That's not to say that marijuana is the new lithium or an all-conquering antidepressant. This is not an argument for 40 grams to freedom. Most psych meds work quite well for an estimated 60 percent to 70 percent of patients. It's the remaining 30 percent to 40 percent who are in a sketchier situation. If the approved meds don't work at all or barely work their alleged magic, where are you supposed to turn?

Psychiatrists usually prescribe another med such as Lexapro, a new antidepressant that's all the rage these days. Personally, I found that marijuana had a positive effect quite by accident, especially when dealing with short-lived psychoses. Medications for that typically take hours or days to work – and when you are in that state, you aren't interested in anything but relief by any means necessary, stat.

So let's assume that weed works for a minority of the mentally ill. Doctors usually come back with the assertion that pot has too many side effects, such as respiratory ailments, to even consider its use. I wonder what universe they live in. Long-term use of psych meds themselves carries a host of side effects, which have been poorly evaluated in long-term studies – kidney and liver damage chief among them, along with nausea, weight gain, sexual dysfunction, sleep interference, and hair loss. And they talk about the side effects of marijuana? By comparison, pot's side effects are almost minimal. So, I'll take that medical marijuana any day – I'd simply like to do it legally.