The Choice of Screening Instrument Matters: The Case of Problematic Cannabis Use Screening in Spanish Population of Adolescents

Table 1

Psychometric properties of the instruments.

(a) DSM-IV abuse criteria

Item	Item basic statistics		Importance of the single item (difficulty)		Internal consistency and discriminative power
	Mean score (points)	SD; (points)	Mean score as percent of mean total score	Frequency of high scoring (%)	Positive on scale if item deleted (%)	Factor loading (CFA)	Cronbach alpha if deleted	Item correlation; /discrimination^a
DSM-IV criteria for abuse: mean total score: 0.46, SD 0.87; Cronbach alpha of scale: 0.613. In principal components analysis, 46.9% variance explained by 1st factor with eigenvalue 1.875.
DSM-1	Sometimes people who use cannabis have serious problems at home, work, or school—such as  (i) neglecting their children, (ii) missing work, or school, (iii) doing a poor job at work or school,  (iv) losing a job or dropping out of school During the past 12 months, did using cannabis cause you to have serious problems like this either at home, work, or school?
	0.15	0.36	32.61	n.a.	21.8	0.685	0.545	0.540
DSM-2	During the past 12 months, did you regularly use cannabis and then do something where using cannabis might have put you in physical danger?
	0.14	0.35	30.43	n.a.	22.7	0.653	0.563	0.483
DSM-3	During the past 12 months, did using cannabis cause you to do things that repeatedly got you in trouble with the law?
	0.09	0.29	19.57	n.a.	26.5	0.705	0.526	0.322
DSM-4	During the past 12 months, did you have any problems with family or friends that were probably caused by your use of cannabis?
	0.12	0.32	n.a.	n.a.	n.a.	n.a.	n.a.	n.a.
DSM-5	Did you continue to use cannabis even though you thought it caused problems with family or friends?
	0.16	0.36	n.a.	n.a.	n.a.	n.a.	n.a.	n.a.
DSM-4+5	The last two items combined to obtain fourth DSM-IV criterion for abuse
	0.08	0.27	17.39	n.a.	26.7	0.694	0.537	0.274

^aFor DSM-IV criteria: proportion of those positive for abuse (at least one criterion fulfilled) who answered the item positively; for CAST: proportion of those with total score 2+ (34.1% of the students fully filling the scale) who had a score of 1 on the item; SDS: item-total correlation.

(b) CAST

Item	Item basic statistics		Importance of the single item (difficulty)		Internal consistency and discriminative power
	Mean score (points)	SD; (points)	Mean score as percent of mean total score	Frequency of high scoring (%)	Positive on scale if item deleted (%)	Factor loading (PCA)	Cronbach alpha if deleted	Item correlation/; discrimination
Cannabis abuse screening test (CAST) scale: mean total score: 1.33 (1.35), SD 1.68 (1.69); Cronbach alpha of scale: 0.762. In principal components analysis, 46.1% variance explained by 1st factor with eigenvalue 2.76.
	Has the following happened to you during the last 12 months?
CAST-1	(a) Have you ever smoked cannabis before midday? 0 = never; 0 = rarely; 1 = from time to time; 1 = fairly often; 1 = very often
	0.24	0.43	18.1	n.a.	29.4	0.722	0.717	0.624
CAST-2	(b) Have you ever smoked cannabis when you were alone? 0 = never; 0 = rarely; 1 = from time to time; 1 = fairly often; 1 = very often
	0.21	0.41	15.8	n.a.	30.7	0.717	0.718	0.549
CAST-3	(c) Have you ever had memory problems when you smoked cannabis? 0 = never; 1 = rarely; 1 = from time to time; 1 = fairly often; 1 = very often
	0.32	0.47	24.1	n.a.	28.1	0.701	0.722	0.732
CAST-4	(d) Have friends or members of your family ever told you that you ought to reduce or stop your cannabis use? 0 = never; 1 = rarely; 1 = from time to time; 1 = fairly often; 1 = very often
	0.20	0.40	15.0	n.a.	31.4	0.726	0.714	0.537
CAST-5	(e) Have you ever tried to reduce or stop your cannabis use without succeeding? 0 = never; 1 = rarely; 1 = from time to time; 1 = fairly often; 1 = very often
	0.21	0.40	15.8	n.a.	30.4	0.542	0.759	0.472
CAST-6	(f) Have you ever had problems because of your use of cannabis (argument, fight, accident, bad result at school, etc.)? 0 = never; 1 = rarely; 1 = from time to time; 1 = fairly often; 1 = very often
	0.17	0.37	12.8	n.a.	31.6	0.645	0.735	0.434

Note: Figures in parentheses relate to calculations after replacing missing values. Displayed only if different from those obtained without applying this strategy.

(c) SDS

Item	Item basic statistics		Importance of the single item (difficulty)		Internal consistency and discriminative power
	Mean score (points)	SD; (points)	Mean score as percent of mean total score	Frequency of high scoring (%)	Positive on scale if item deleted (%)	Factor loading (CFA)	Cronbach alpha if deleted	Item correlation/; discrimination
Severity of dependence scale (SDS): mean total score: 1.57 (1.56), SD 2.42 (2.42); Cronbach alpha of scale: 0.672. In principal components analysis, 45.6% variance explained by 1st factor with eigenvalue 2.28.
SDS-1	In the last 12 months, (1) did you ever think your use of cannabis was out of control? 0 = never or almost never; 1 = sometimes; 2 = often; 3 = always or nearly always
	0.28	0.73	17.83	4.7	12.6	0.67	0.61	0.67
SDS-2	(2) Did the prospect of missing a smoke make you very anxious or worried? 0 = never or almost never; 1 = sometimes; 2 = often; 3 = always or nearly always
	0.23	0.58	14.65	1.9	13.6	0.757	0.596	0.678
SDS-3	(3) Did you worry about your use of cannabis? 0 = not at all; 1 = a little; 2 = quite a lot; 3 = a great deal
	0.31	0.68	19.75	2.9	11.4	0.761	0.562	0.741
SDS-4	(4) Did you wish you could stop? 0 = never or almost never; 1 = sometimes; 2 = often; 3 = always or nearly always
	0.51	0.98	32.48	10.3	9.7	0.563	0.680	0.683
SDS-5	(5) How difficult would you find it to stop or go without cannabis? 0 = not difficult; 1 = quite difficult; 2 = very difficult; 3 = impossible
	0.24	0.65 (0.64)	15.29	2.8	13.3	0.602	0.655	0.566

Note: figures in parentheses relate to calculations after replacing missing values.