A commercial driver's license (CDL) is a driver's license required in the United States to operate any type of vehicle. 1  weighing 26,001 pounds or greater, or any combination of vehicles weighing 26,001 pounds or greater when towing a trailer weighing more than 10,000 pounds.
The cause of drug abuse is not fully known but likely include genetic predisposition, co-occurring conditions and environmental circumstances. Drug use and experimentation is common in pre-adolescents and adolescents, but only a small percentage of those users will go on to abuse drugs.hile many people use drugs, only a small percentage abuse drugs, but it has been noted drug abuse often runs in families, suggesting genetics is one of the causes of drug abuse.
The precise causes of chemical dependency are unknown. However, there are factors that can cause a person to have a higher risk of drug or alcohol addiction. Genetic factors play a role in addiction, and someone with a family member who has chemical-dependency issues may be at higher risk.any different substances can be abused, and people can develop an addiction to many of these drugs. Some of the most commonly used and abused chemical substances include: 1  Alcohol. 2  Marijuana. 3  Stimulants, such as cocaine, methamphetamine, and amphetamines. 4  Hallucinogens, such as LSD, mescaline, PCP, and psilocybin.