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Not all smokers get lung cancer. And some people can quit more easily than others. Some of the reasons may be genetic, new research shows. The studies found different versions of genes that increase the risk of both lung cancer and smoking addiction. Smokers who get the gene variants from one parent have a 30% greater risk of lung cancer. The risk goes up 80% for smokers who get the genes from both parents. Another study found that people with these genes get addicted more easily and smoke more. Three different studies found the variant genes on chromosome 15. USA Today and the Associated Press wrote about the studies April 3. They were published in the journals Nature and Nature Genetics.

Treating children early for attention deficit-hyperactivity disorder (ADHD) does not raise their risk of drug abuse, a study finds. But starting treatment later may increase that risk. The 17-year study included 176 boys with ADHD. All were treated with stimulant medicines. They received Ritalin or a generic version of it. Some boys started taking it at ages 6 or 7. They went on to have no more drug abuse problems than a comparison group of healthy children. But boys who began treatment at ages 8 to 12 did have higher drug abuse rates later on. The study was published April 1 in the American Journal of Psychiatry.