Hard drugs
Cocaine (in powder form or in smokable form as crack), the amphetamines, and the opioids such as heroin and morphine, are most commonly referred to as hard drugs. According to researchers, medical evidence indicates that alcohol and nicotine, while freely available for sale in many countries, should be described as hard drugs as well because they are both addictive, associated with high mortality rates, and cause significantly more damage to the body than virtually all illegal drugs when compared scientifically (for example pharmaceutically pure or even reasonably purified street heroin, when consumed following a few basic safety rules, actually causes no harm to the body, even when taken over years or decades, while alcohol use is associated with liver and brain damage but is only age-restricted). In most popular discourse, however, hard drugs refers to drugs illegal for nonmedical use associated with highly visible problematic users, in the United Kingdom these are predominantly heroin, cocaine, and methamphetamine.
Soft drugs
The term soft drug is most usually applied to cannabis (marijuana or hashish) because it is not associated with deaths, crime or violence amongst users and is without evidence of physical addiction. This distinction between soft drugs and hard drugs is important in the drug policy of the Netherlands, where cannabis production, retailing and use come under official tolerance (NL gedoogbeleid), subject to certain conditions. Other psychedelic drugs such as psilocybin and LSD are also considered soft drugs by many because there is no evidence of physical addiction and it is nearly impossible to overdose on these drugs. There have been no human deaths recorded from the use of psychedelics (with the exception of MDMA, which has produced no overdoses).
Hallucinogens
Some consider certain hallucinogens to be hard drugs, but as most hallucinogens are non-addictive, nor are they known for causing deaths, such drugs generally occupy a middle ground - neither hard nor soft. The possible exceptions are PCP, DXM and the phenethylamine-based empathogens such as MDMA, many of which are closely related to amphetamines; being relatively new to the drug culture more research is needed to ascertain the addictive potential and potential harms of these drugs.
The drug policy of the Netherlands classifies synthetic hallucinogens such as LSD (acid) and MDMA (ecstasy) as hard drugs, although they have very similar action to naturally occurring drugs such as mescaline, which is considered a soft drug in its natural form of peyote, or psilocybin in its natural form as psilocybe (magic mushrooms). Both are sold legally in the Netherlands in their unprocessed natural form.