I read infrequent pot smokers are 40% more likely to develop psychosis, mathematically, what does this mean?

Question

If an infrequent user is 40% more likely to develop psychosis than a non user, does this mean that 40% of all persons diagnosed as psychotic has a history of infrequent use? It also said that frequent users are 200% more likely to develop psychosis. Does this mean 200% of all persons diagnosed to be psychotic were frequent users? That doesn't make sense, and I'm not really good with math, can you explain what these percentages mean, and how they got those numbers? Thanks!

Answer 1

If this study is comparing non-pot smokers to smokers then:

if you had 2 groups of 100 persons and the first group of 100 was non pot smoking while the other 100 were infrequent users, then however many are diagnosed as psychotic in the first group, there is 40% more in the second group. So multiply the number in the first group by 1.4 to get the number in the second group.

If there are 10 in the first group of non users then there are 14 in the occational users group.
Layman translation:
there is always more people who can be diagnosed as psychotic in a non smokers group, and there is almost half as many more in the occasional smokers group as a non smokers group and there are twice as many in a frequent user group than a non user group.

So if in a group of 100 non pot smokers there are 20 diagnosed as psychotic, then the occasional group has 28 and the full time potheads are 40.

The base percentage of people diagnosed as psychotic, in a non user group shold be given first, for you to calculate the subsequent percentages.

Moral of the story, pot is bad for you if you are an occational user and even worse if you do it mor often.

Answer 2

It means:

Let x = all of the non-users in the study.

Let y = all of the infrequent users in the study.

Let z = all frequent users in the study.

Let T = the total population participating in the study. Everyone in the study has been diagnosed with pschosis.

T = x + y + z

T = x + 1.4x + 3x (because of the use of the word "more", you have to add the percents to 100%)

If you take all of the non-users (x) and you multiply that by 140%, that will give you the number of infrequent users.

If you take all of the non-users and multiply that by 300%, that will give you the number of frequent users.

For instance, if the number of non-users is 50, then the number of infrequent users is 70, and the number of frequent users is 150.

The total population is 50 + 70 +150 = 270.

In this example, of the 270 pyschotic people in this study, 50 were non-users, 70 were infrequent users, and 150 were frequent users.

roughly:
50 / 270 = 19%
70 / 270 = 26%
150 / 270 = 56%

This shows that 56% of the psychotic people in this study were frequent pot smokers. 26% were infrequent users and 19% didn't touch the stuff.

Answer 3

No, that is not correct.

What it means is this:

From the population of non-smokers, suppose 0.01 % develop psychosis. The percentage goes up to 0.014 % for infrequent smokers and to 0.02% for frequent users.