Table 1 Scales included in the analysis

Severity of Dependence Scale (SDS)

Five-item questionnaire measuring psychological dependence on different illicit drugs. A score from zero to three is used for each item, and then totalled (Lawrinson, Copeland, & Indig, 2005). If a cut-off score greater than three is measured, this is an indication for problematic alcohol use (Lawrinson, Copeland, Gerber, & Gilmour, 2007). If a cut-off score greater than four is measured, this is an indication for problematic drug use (Martin, Copeland, Gates, & Gilmour, 2006; Topp & Mattick, 1997).

0 = never/almost never

1 = sometimes

2 = often

3 = always/nearly always

The scores are added together. The higher the score, the more problematic drug use.

General Functioning Scale

A sub-scale of the Family Assessment Device (FAD), which consists of 12 items that measure the overall functioning and health of a family (Byles, Byrne, Boyle, & Offord, 1988; Epstein, Baldwin, & Bishop, 1983). A score is given to each item from one to four, depending on the individual’s response to a certain statement, which is then averaged. A total score of two or more is considered as problematic family functioning, where the higher the score, the more problematic the family’s overall functioning (Byles et al., 1988).

A 4-point Likert Scale is used, which includes 4 options: strongly agree, agree, disagree and strongly disagree. The responses for each measure are added and the total is divided by the number of items in each scale. The higher the score, the worse the levels of family functioning.

Social Functioning Scale (SFS)

Consists of six items measuring levels of social conflict and financial hardship, time spent with drug users and non-drug users and involvement in criminal activity (Lawrinson et al., 2005). A scoring from zero to three is provided and then summed. A higher score represents a greater degree of social dysfunction (Darke, Hall, Wodak, Heather, & Ward, 1992; Epstein et al., 1983; Lawrinson et al., 2005).

A scoring from zero to three is provided for each question, where all scores are summed. Some answers my not be applicable to some people so a coefficient based on non-applicable answers is multiplied by the sum-total (Darke et al., 1992; Epstein et al., 1983; Lawrinson et al., 2005).