Cannabis Smoking in Teenagers


  1. Cannabis smoking disrupts the hormonal balance in both men/boys and women/girls. We do not know exactly how this affects teenagers, but the suspicion is that it can reduce fertility. There have been reports of disturbance in growth and of delayed sexual maturity.
  2. Cannabis as a gateway to harder drugs: It has long been understood that cannabis use is one of several factors that increase the likelihood of starting to use other illegal drugs. One of the reasons for assuming there to be a causal connection has been that the intensity and duration of a person’s cannabis smoking increase the risk that he or she will move on to harder drugs. Notwithstanding this, it is only recent and methodologically well-conducted studies (including prospective ones of long duration covering a large number of people) that have been able to show that, even after controlling for the effects of other known and suspected factors, there remains a strong association between cannabis smoking and moving on to harder drugs. It would appear that we are close to proving the controversial gateway hypothesis the hypothesis that, in many cases, cannabis use constitutes a gateway to harder drugs.
  3. The development of identity, according to accepted theory and experience, is a central aspect of the psychological development of young people. In turn, the development of identity is crucially dependent on a number of other factors, including certain aspects of cognitive development – which, as we know (see above), is put at risk by long-term cannabis smoking. A large number of clinical reports and a few extensive scientific studies also show that when a person uses cannabis, this is often one of the reasons why psychosocial teenage development slows down, comes to a standstill or even breaks down completely.

The Sensitive Teenage Years

This is the most important chapter of this report. With most drugs – not least cannabis – the teenage years are of special importance. Vulnerability to various side-effects is generally highest in teenagers. Exposure to cannabis is also highest in the teenage years, as the early peer group takes on greater importance and a range of factors may tempt young people to “feel their way” and “just try it”.

Naturally, most of what is discussed in other chapters applies to teenagers as well. Therefore, this chapter looks mainly at those harmful effects that have specific importance in the teenage years. This often means the effects that interact with the teenager’s “developmental tasks” – the expectations that people around them (from parents to psychologists and sociologists) tend to subsume under headings such as “breaking free from one’s parents”, “finding oneself ”, “finding one’s identity”, “finding a way to relate to the other sex”, “finding the meaning of life”, “conquering a new social arena – from the teenage peer group to a circle of adults” and “choosing and starting a career”. Or, quite simply, leaving – not without a certain sadness – childhood and maturing into an adult.

Database searches yield no avalanche of studies that deal with this complex of problems – the teenager’s encounter with cannabis abuse. Of course, there are on-going research projects, and the annual number of reports published in scientific articles seems to be on the increase at present. These reviews contain no sections on teenagers and cannabis. It is especially remarkable that the otherwise excellent Cannabis and Health Hazards (1983) does not devote a section to this issue; and it is perhaps even more surprising that no mention is made of this fact in the foreword. Similarly, there is no such section in the WHO’s most recent publication, The Health Effects of Cannabis (1999).

The Health and Psychological Consequences of Cannabis Use (1994) represents an exception in that its authors discuss, in an integrated manner, the issue of the effects caused by cannabis on different aspects of youth development.

The “failure” of the other reports might be attributable to the fact that it is taken as a given that cannabis is a young people’s drug. It might also be that our culture’s bad conscience has put blinkers on the editors and authors. Perhaps this is just another reflection of our society’s inability to see the needs of young people and to take these needs into account?

To be fair, though, it must immediately be said once again that research teams all over the world have devoted decades to the youth-related issues. Denise Kandel and her co-workers constitute one of the best-known such teams.

This seemingly low-key interest from parts of the research community stands in stark contrast to the numerous worrying clinical observations concerning young people’s relationship to cannabis. For example, at the Maria Ungdomsmottagning in Stockholm (a clinic specialising in young abusers), the impression gained by the staff is that it is, in fact, often easier to help a young heroin addict than it is to help a firmly addicted cannabis abuser. The reason why parents’ anti-drug associations in e.g. Sweden and the United States have taken such a strong stand against cannabis is that they have seen so many cases where a teenager’s development has come to a halt as a result of long-term hashish or marijuana smoking.

This chapter will deal with three aspects of the effects caused by cannabis abuse on the teenage individual:

  • The effects of cannabis on the hormonal system during the teenage years
  • Does cannabis abuse represent a gateway to harder drugs?
  • Cannabis abuse and the teenager’s psychosocial maturation

The Effects of Cannabis on the Hormonal System during the Teenage Years

As is shown in the post on fertility (), cannabis can affect the hormonal balance in both men and women. However, this effect seems to be more relevant in men. The changes in hormonal balance which cannabis can provoke are suspected of being involved in a relative reduction of fertility in adult men. There is reason to suspect that such hormonal effects may be more important during puberty than later on in life. As is also pointed out in the chapter on fertility, gynaecomastia (development of breasts in men) has been observed in a small number of men who were intensive smokers of cannabis (). The importance of these findings is uncertain. If intensive cannabis smoking in men always caused a hormonal imbalance resulting in gynaecomastia, this phenomenon ought to be better known both to the public and in the research community.

There is one reported case concerning a 16-year-old boy who had smoked marijuana since the age of 11. He was short in stature and had no pubic hair, his testicles and penis were small, and his blood testosterone level was low. When he stopped smoking, he started growing again and his blood testosterone increased to a normal level (). Although this observation refers to a single case, it ought to be seen as providing a warning signal, bearing in mind the occasional reports of children starting to smoke cannabis at a very young age.

In women, the menstrual cycle is affected. Taken together with findings from animal experiments, this is considered to suggest that cannabis can bring about a relative reduction of fertility.

To sum up, we know that continual cannabis smoking disrupts the hormonal balance of the body. The effects of this disruption include a lowering of testosterone levels in men/boys and disturbances to the hormones which control the menstrual cycle in women/girls. While we do not know exactly how this affects teenagers, we suspect that it may disrupt sexual maturity and fertility, and possibly growth as well.

Does Cannabis Abuse Represent a Gateway to Harder Drugs?

Cannabis Abuse and the Teenager’s Psychosocial Maturation

Clinical Experience

In addition to accounts given of their experience by field-workers, doctors and nurses, teachers, police officers and not least parents, there are also more systematised and detailed descriptions of the long-term effects produced by cannabis on teenagers – for example textbooks (), a section of a research report () and a clinical report in a scientific journal (). Kerstin Tunving, a very experienced doctor in the field of drug-addiction treatment, wrote the following in her article Psychiatric Aspects of Cannabis Use in Adolescents and Young Adults ():

To sum up, the impression is, based on clinical observations, that teenagers who abuse cannabis “sleep away” their teens. They often do not develop at the same pace as youth of the same age, but stay childish and dependent.

It is also of interest to note that what induced Richard Schwartz and his co-workers to conduct a study into the effect of cannabis on short-term memory in young people was, in fact, repeated clinical experience of cannabis-dependent young people who, when admitted to a treatment programme, found it very difficult to remember information and instructions during the first three or four weeks.

Scientific Studies

In addition to the previously mentioned problems involved in carrying out studies of this kind, it should also be noted that two of the studies described here were carried out in the United States in the 1970s and early 1980s, when the American market was still dominated by weaker cannabis preparations. Moreover, none of the studies makes any attempt to correlate outcome with varying intensity of cannabis abuse ().

In the introductory chapter of their large study Living High, Hendin et al. sum up their findings from earlier studies of cannabis-smoking teenagers:

In all of its functions marijuana served to detach these adolescents from the problems of the real world – from their anger and unhappiness with their parents and from the need to work and compete to achieve success […] Fantasies of being destined for a special fate, to become rich without work, and to excel at a sport they scarcely played were typical of the parody of success, achievement, and confidence that marijuana sustained in some of the young men […] The young female marijuana abusers, although not usually expecting particular greatness, nevertheless maintained a magical belief that good things would happen to them: college acceptance while flunking out of high school, or happiness in love while dating unresponsive or abusive young men. For all these adolescents, marijuana helped sustain in an unrealistic way the desire for power, control, achievement and emotional fullness (Hendin).

In her dissertation The Prognosis of Drug Abuse in a Sixteen-Year-Old Population, Maj-Britt Holmberg () studied over 1,000 Swedish pupils in the ninth year of school (aged 15–16). Of these, 14 per cent used cannabis (primarily). At a follow-up after eleven years, she found the following:

  • The mortality rate was 5–8 times higher among those who were abusers at the time of the first interview in the ninth year of school.
  • The abusers (together with those who had attended remedial classes or had left school prematurely) had had an above-average level of medical and social problems during their childhood and youth.
  • Of the drug users, 10 per cent had been diagnosed as having a psychosis during the eleven-year follow-up period.
  • The 2.4 per cent who had claimed a highly frequent use of drugs (with cannabis being the dominant drug) were more likely to develop drug addiction proper than the other abusers.

The most extensive and in-depth longitudinal study of young cannabis smokers carried out to date was conducted by Michael Newcomb and Peter Bentler (). In their main report, they concentrate on the effects of cannabis use on individuals’ entry into young adulthood. They studied the consequences of use/abuse of alcohol, marijuana abuse and the abuse of hard drugs. In many respects, the three categories of drugs produced similar effects.

The findings reported include the following:

– Cannabis smoking increased the risk of impairment to mental functions in young adulthood. The researchers measured a higher degree of “psychoticism” and a reduced ability to make careful plans. “This effect […] indicates that teenage drug use interferes with organized cognitive functioning and increases thought disorganization into young adulthood.”

– Only the use of hard drugs was found to be associated with an increase in suicidal thoughts during young adulthood. (See, however, the above section on the risk of transition from cannabis to hard drugs.)

– Smoking cannabis as a teenager was shown to have a clear association with a number of negative psychosocial factors during the teenage years, but above all during the early stages of adult life. The abusers in this study, like those in e.g. Kandel’s () study, were more likely to interrupt their training or education. Once they reach adulthood, abusers exhibit less stability on the labour market – i.e. they find it harder to hold down a job.

– Further, the abusers showed a significantly stronger tendency to fail in their marriages, as expressed in a higher divorce frequency. – Finally, it was found that the social networks built by the abusers during these early years of their adult lives were worse than those of the non-abusers.

Newcomb and Bentler () conclude that their large-scale study supports, in a number of respects, Baumrind and Moselle’s theory that abuse (of e.g. cannabis) during the teenage years leaves teenagers less well equipped to integrate themselves into adult life.

Moreover, these data are supported in most respects by the analysis of young New Zealanders carried out by Fergusson and co-workers within the – over ten years more recent – Christchurch Study (). In the most recent report (after monitoring their 1,265 pupils/young adults up to the age of 21), the researchers sum up their findings as follows:

Cannabis use, and particularly regular or heavy use, was associated with increased rates of a range of adjustment problems in adolescence/young adulthood – other illicit drug use, crime, depression, and suicidal behaviors – with these adverse effects being most evident for school-aged regular users.


Selections from the book: “Adverse Health Consequences of Cannabis Use. A Survey of Scientific Studies Published up to and including the Autumn of 2003