When Bad Meth Trips Never End

"There is also a theory that drug abuse "resets" the reward pathway, making it more difficult to experience reward or well-being from normally pleasurable experience, Miotto says.

Unfortunately, Cross did not escape this part of methamphetamine addiction.

"I'm not the same person, I can tell you that," said Cross, whose biggest regret was the time drugs took away from her five young children.

"I was a fun-loving person," she said. "I suffer now more from depression."

All Highs Come With a Risk

Meth users make up only 0.3 percent of the U.S. population, according to the 2006 National Survey on Drug Use and Health.

But the 8 percent of people who use other drugs aren't necessarily free from permanent mental health affects.

In the summer, a study in the journal Lancet found that marijuana can increase an individual's risk of developing a psychosis by 40 percent, and possibly up to 200 percent, depending on how long and how much a person used.

The greater a person's risk to develop a psychosis like schizophrenia, the more dangerous it is to use marijuana.

Marijuana may also exacerbate an underlying mood disorder like anxiety, depression or bipolar disorder.

"Those are often the chicken-and-the-egg questions: If people who have depression or anxiety -- symptoms of a mood disorder -- are more likely to use marijuana in the first place," Miotto said.

No Safe Place

For Jim Morrison, 55, the question of the chicken or the egg may never be answered. He started using marijuana at 16 and was diagnosed with bipolar disorder at age 40.

Morrison, the webmaster of the addiction support Web site, mysobrietyspace.com, has been sober for 28 years. But for the better part of a decade, his drug use came with emotional mood swings and occasional paranoia.

"Once I quit drinking or getting stoned, the manic depression episodes got much better,"Morrison said.

At one point in 1979, Morrison became so paranoid about his drug use that he was convinced the Newport Beach, Calif., SWAT team was waiting at his apartment to bust him for an ounce of marijuana.