With the legalization of marijuana by District voters this month, the fun begins for some, and pitfalls begin for others. As the kinks are worked out before the distribution and sales arrangements are unveiled, we can look at what we have gotten ourselves into.

The legalization of pot takes marijuana out of the shadows, removing it from the black-market economy that fosters further criminal activity. It could potentially allow the government to monitor its use and sales and to tax these sales. It eliminates a whole category of criminal trials and incarcerations.

Another benefit may be a reduction in alcohol-impaired driving. Colorado has seen a significant decrease in alcohol-related traffic deaths since the legalization of marijuana took effect in January.

Yet there are major downsides. Regular marijuana use, particularly daily, affects motivation and ambition. Marijuana, maybe more than other drugs, helps people care less. But caring is an important emotion. And learning to care less without drugs is a valuable coping skill. As a psychiatrist, I have seen men and women in their 30s and 40s wondering what they could have accomplished had they not been smoking weed daily as teenagers and young adults. Ambition and motivation are terrible things to waste. We have no way of measuring motivation. But, as with pornography, we know it when we see it — and when we don’t.

Also, marijuana is addictive — not as much as cocaine or opiates but addictive nevertheless. Some people confuse addictiveness, physical dependency and tolerance. Marijuana does not cause a physical dependency. It does not have a physical withdrawal syndrome, unlike withdrawal from alcohol or opiates. And it does not produce increased tolerance to its effects over time.

Marijuana follows the same principles of any other addictive drug. Consider the principle reflected in a Japanese proverb initially applied to alcohol: “First the man takes a drink, then the drink takes the drink, then the drink takes the man.” Likewise, anyone who smokes weed long enough will reach a point at which the marijuana is smoking him. The chemicals in cannabis attach to the cannabinoid receptors in the human brain, and we can become chemically addicted to external cannabinoids — marijuana.

Unfortunately, it is unrealistic to create a legal age for inhaling weed of 35 or 40 — the age at which people might be able to use marijuana responsibly, without a huge effect on their lives. The law passed in the District allows for smoking and absorbing marijuana products at age 21, just as with alcohol. At the very least, however, we should discourage its regular and daily use until later adulthood.

Prohibition of alcohol did not work in the early 20th century; perhaps prohibition of marijuana makes no sense either. Still, despite my usual decisiveness and despite my knowledge of the issue, I found myself freezing up in the voting booth on Nov. 4. I easily could have voted either way. I ended up voting against legalization because I could not help but think of all the teenagers and young adults who would learn to consider marijuana innocuous, who would not learn naturally how to care less and who might become addicted to daily pot use and lose motivation and ambition.

In whatever way we unveil the legal use of marijuana, let’s make sure we do not create future generations of genuine slackers.

The writer is a psychiatrist.