The long-term effects of cannabis have been the subject of ongoing debate. Because cannabis is illegal in most countries, research presents a challenge; as such, there remains much to be concluded. The long-term effects of cannabis have been the subject of ongoing debate. Because cannabis is illegal in most countries, research presents a challenge; as such, there remains much to be concluded. Acute cannabis intoxication has been shown to negatively affect attention, psychomotor task ability, and short-term memory. Studies of chronic cannabis use have not consistently demonstrated a long-lasting or refractory effect on the attention span, memory function, or cognitive abilities of moderate-dose long-term users. Once cannabis use was discontinued, these effects disappeared in users abstinent for a period of several months. Chronic use of cannabis during adolescence, a time when the brain is still developing, is correlated in the long term with lower IQ and cognitive deficits. It is not clear, though, if cannabis use causes the problems or if the causality is in the reverse. Recent studies have shown that IQ deficits existed in subjects before chronic cannabis use, suggesting that lower IQ may instead be a risk factor for cannabis addiction. Cannabis is the most widely used illicit drug in the Western world, and although in the United States 10 to 20% of consumers who use cannabis daily become dependent, it is different from addiction. Cannabis use disorder is defined in the fifth revision of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) as a condition requiring treatment. A 2012 review of cannabis use and dependency in the United States by Danovitch et al said that '42% of persons over age 12 have used cannabis at least once in their lifetime, 11.5% have used within the past year, and 1.8% have met diagnostic criteria for cannabis abuse or dependence within the past year. Among individuals who have ever used cannabis, conditional dependence (the proportion who go on to develop dependence) is 9%.' Although no medication is known to be effective in combating dependency, combinations of psychotherapy such as cognitive behavioural therapy and motivational enhancement therapy have achieved some success. Cannabis dependence develops in 9% of users, significantly less than that of heroin, cocaine, alcohol, and prescribed anxiolytics, but slightly higher than that for psilocybin, mescaline, or LSD. Dependence on cannabis tends to be less severe than that observed with cocaine, opiates, and alcohol. A 2018 review of the nature of dependency on marijuana states that the risk of dependence formation among regular marijuana consumers has declined since 2002. Historically, the possible connection between psychosis and cannabis has been seen as controversial. Medical evidence strongly suggests that the long-term use of cannabis by people who begin use at an early age display a higher tendency towards mental health problems and other physical and development disorders, although a causal link is not established. These risks appear to be most acute in adolescent users. Cannabis can contain over 100 different cannabinoid compounds, many of which have displayed psychoactive effects. The most distinguished cannabinoids are ∆9 – THC (THC) and cannabidiol (CBD), with THC being the primary agent responsible for the psychoactivity of cannabis. The effects of THC and CBD are salient regarding psychosis and anxiety. As of 2017 there is clear evidence that long term use of cannabis increases the risk of psychosis, regardless of confounding factors, and particularly for people who have genetic risk factors. Numerous studies have been conducted regarding anxiety and cannabis for therapeutic purposes, and these cross-sectional studies have been mostly consistent regarding the anxiolytic effects. The studies showed relief of anxiety as a result of cannabis consumption.