See and who also show that there is a higher risk of failing to complete high school or post-secondary school among cannabis users who start using early.Furthermore,like many other researchers, claim that early and frequent use of marijuana has a significant negative effect on psychological health. Shubart et al. showed that individuals who start using marijuana after the age of 18 do not see as great a negative effect on mental health in terms of psychotic experiences, but rather it’s the individuals who start using earlier than that, especially as early as 12 years old who suffer much more. Another study by showed similar findings; a 15 year follow up of over 50,000 Swedish military personnel revealed that those who tried cannabis before the age of 18 were 2.4 times more likely to develop schizophrenia than those who did not. After an adjustment for a history of mental illness and personal adverse conditions like parental divorce, they found that those who used at least 10 times before the age of 18 were 2.3 more times likely to develop schizophrenia.
Physical health is also a concern with early age of first cannabis use. The literature shows that risk of physical illnesses is significantly lower among cannabis users than among tobacco users but frequent cannabis use can cause chronic respiratory problems,mainly bronchitis, . Lev-Ran et al.analyzed American cross-sectional data and used a quality of life variable based on the self-reported SF-12 summary scale.3 Scores are based on an item response model. This contains a physical component summary score and a mental component summary score that are derived from the survey. Like other researchers, they found that cannabis users had lower scores for MCS than those of non-users, but surprisingly a higher score of PCS. Physical symptoms as they are related to cannabis use are the least discussed in the literature. McLeod et al, for example, dismissed the physical harms of cannabis as they were not as significant as the psychological ones; see this paper for more examples of similar findings. Many of the studies referred to earlier show higher probabilities of both physical and mental illness as a consequence of early and repeated use of marijuana.
These results are often based on longitudinal databases and refer to samples of older respondents. To assess the impact of marijuana use especially on younger respondents a measure, which can be applied to respondents regardless of their age, is needed. Questions, which ask respondents to reveal how they feel or whether they are experiencing certain physical or psychological difficulties can be put to respondents even when they are teenagers. As will be seen below, marijuana use by this age group is crucial in understanding what happens to respondents in older age groups. The Canadian survey simply asks respondents to indicate the current state of their physical and mental health using a five point scale which goes from poor to excellent. This appears to produce reliable results even when the respondents area dolescents.4 Responses by age and gender are shown in Table1.Generalizations of this approach are sometimes used. The World Health Organization disability assessment schedule, the Kessler psychological distress score,and the 12 item health survey ,, which is contained in the National Epidemiological Survey of Alcohol and Related Conditions all use supplementary questions to bring more precision to the notion of how individuals regard their mental health.Their questions are also on a five point scale going from 0 to 4, which is the worst state possible. The first two scores are just the sum of the answers making the scores run from 0 to 24.
This procedure is somewhat crude since differences in states are constrained to be equal and all items have the same weight. A more reliable procedure is used for analyzing the SF-12 data is used by ; it used an item response model to summarize the information contained in the items.The use of self-reported health indicators has a long history of being a reliable indicator of current health status. For a summary of the literature, which evaluates its performance see.There are14,555 respondents in the first survey, and adolescents are over-sampled. The proportion of the sample 21 or younger is 32.6%. There are two endogenous variable of interest.These are “self-reported physical health” and “self-reported mental health”. Both of these variables are categorical with five outcomes running from poor to excellent. Explanatory variables include current smoking behavior whose three categories are smoking cigarettes every day, occasionally, or not at all. Age of first daily use of alcohol and marijuana are included. Alcohol use is described by an eight category variable describing drinking behavior over the last twelve months. This runs from daily or almost daily to less than once a month. The residual category is never.