Table 1.

Prevalence of Endorsed Items From CIDI Regarding Cannabis Use and Symptoms of Cannabis Use Disorders Among 2793 Young Adult Norwegian Twins

Item	Item Content	Response Categories	n	%
L3A1	Have you ever taken cannabis?	1	289	10.4
L3B1	Have you ever taken cannabis 5 times or more?	1	201	7.2
		1a	46	1.7
		2b	28	1.0
L7	In the period when you were using cannabis most frequently, how often did you use it?	3c	31	1.1
		4d	38	1.4
		5e	57	2.0
L9A	Have you ever felt such a strong desire or urge to use cannabis that you could not keep from using it; or did you ever want cannabis so badly, that you could not think of anything else?	1	19	0.7
L10A	Have you ever tried to stop taking cannabis altogether, but found you couldn’t or have you ever had the continual desire to reduce your consumption?	1	17	0.6
	Have you already tried several times or had the continual desire to reduce your use of cannabis or stop taking it altogether but found you couldn’t?	2	10	0.4
L11A	If you took less cannabis than you normally did or didn’t take any, did you have any of these problems (list of withdrawal symptoms)?	1	35	1.3
L11C	Did you ever take cannabis in order to make these problems (list of withdrawal symptoms) go away or to keep from having them?	1	22	0.8
L12A	Has there ever been a period when you spent a great deal of time using or getting over the effects of cannabis?	1	20	0.7
L13A	Have there often been times when you used more cannabis than you intended to or when you used cannabis for a much longer period than you intended to?	1	35	1.3
L14A	Did you ever find that you had to use much more cannabis than before to get the effect you wanted or did you ever find that the same amount had less of an effect on you than it once did?	1	30	1.1
L15A	Have you ever given up or greatly reduced important activities in order to get or to use cannabis – activities like sports, work or associating with friends?	1	19	0.7
L16A	Has taking cannabis ever caused you any medical problems?	1	5	0.2
L17A	Has taking cannabis ever caused you any emotional or psychological problems – such as being uninterested in your usual activities, being depressed, suspicious or distrustful of other people, or having strange thoughts?	1	32	1.2
L17C	Did you continue to use cannabis after you realized it was causing you any of these emotional problems?	1	21	0.8
L19E	Did you ever have considerable problems with your family or friends because of your taking cannabis [OR] Did your taking cannabis ever cause the break-up of a relationship you’re your partner, a family member or friend [OR] Did you ever get into financial difficulties because of your taking cannabis [OR] Have you ever attacked someone or injured them while under the influence of cannabis?	1	16	0.6
	Did you ever have any of these kinds of problems more than once in connection with your taking cannabis?	2	5	0.2
L20A	Have there been several times when you were under the influence of cannabis, or suffering from its after-effects when that increased your chances of getting hurt – for instance when riding a bicycle, driving a car or boat, operating a machine, or anything else?	1	20	0.7
L21A	Has taking cannabis ever caused considerable problems with your family, friends at work or at school (for example, repeatedly staying home from work/school, poor performance, expulsion from school, neglecting of children and the household)?	1	18	0.6
L22A	Did your use of cannabis ever lead to you getting into trouble with the police more than once, for example, for possession of drugs, theft in order to obtain the substance or driving under the influence?	1	16	0.6
L23A	Have you ever accidentally injured yourself, that is, had an accident or a bad fall while under the influence of cannabis?	1	4	0.1

Note: CIDI, Composite International Diagnostic Interview.

^aLess than 1 day a month.

^b1–3 days a month.

^c1 or 2 days a week.

^d3 or 4 days a week.

^eAlmost daily.