Here are some of the latest health and medical news developments, compiled by the editors of HealthDay:

Teen Drivers' Marijuana Use Causes Concern

Teens who drive while high on marijuana appear to be a growing problem.

Pot smoking is up among teens and use of the drug among high school students is higher than it has been in three decades, finds new survey data compiled by Students Against Destructive Decisions (SADD) and the insurance industry, the Washington Post reported.

Survey results also show that 19 percent of teens said they'd driven a vehicle while stoned, and more than one-third said marijuana causes no distractions to their driving, according to the information released Wednesday.

"What keeps me up at night is that this data reflects a dangerous trend toward the acceptance of marijuana and other substances compared to our study of teens conducted just two years ago," Stephen Wallace, senior adviser for policy, research and education at SADD, told the Post.

Last week, the Governors Highway Safety Association said that teen highway deaths increased in the first half of 2011, reversing an eight-year downward trend.

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Male Y Chromosome Won't Vanish: Study

Men's Y chromosome may not wither away to nothing after all, according to a new study.

The male Y and female X chromosomes once had about 800 genes in common but the Y now carries just 19 of its ancestral genes, along with its male-determining gene, and is just a fraction of its original size, The New York Times reported.

This has led some scientists to wonder if the Y chromosome will eventually vanish and make human males a thing of the past.

But a new study suggests that the Y chromosome's gene-shedding is finished and it will shrink no more, The Times reported.

The study was published Wednesday in the journal Nature.

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State Can't Force Pharmacies to Sell Emergency Contraceptives: Judge

Washington state cannot force pharmacies to sell Plan B or other emergency contraceptives, a federal judge ruled Wednesday.

State regulations require pharmacies to stock and dispense drugs for which there is a demand. The regulations were implemented in 2007 after reports that some women in the state were denied access to Plan B, the Associated Press reported.

A pharmacy and two pharmacists filed a lawsuit that said the rules infringed on their religious freedom. U.S. District Judge Ronald Leighton agreed with them.

The judge ruled that the intent of the state regulations was not to promote timely access to medicine, but to override religious objections by pharmacists who believe that emergency contraceptives have an effect that's similar to abortion, the AP reported.

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U.S. Releases Draft Strategy to Fight Alzheimer's Disease

Finding effective ways to treat Alzheimer's disease by 2025 is the main goal of the Obama administration's draft of a national strategy to fight the disease.

That could be a huge challenge. Current treatments only temporarily ease symptoms of Alzheimer's and efforts to develop better medications have been slow, the Associated Press reported.

The draft also recommends improved training and support for caregivers of loved ones with Alzheimer's, campaigns to raise awareness about the early warning signs of the disease, increased education for doctors and other health care providers, and improved early detection of Alzheimer's.

The draft was released Wednesday and is open for public comment through March. The final strategy will be released this year, the AP reported.

More than 5 million Americans have Alzheimer's or similar dementias and that number is expected to reach as many as 16 million by 2050.

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