Spoth 2001 (ISFP).

Methods	Country: USA Site: 33 rural schools in 19 contiguous counties in a Midwestern US state [Iowa] 'Iowa Strengthening Families Program' (ISFP) and 'Preparing for the Drug Free Years Program' (PDFY) Focus: tobacco, alcohol, marijuana prevention Design: cluster RCT (Group 1: never smoking prevention cohort / Group 2: change rates)
Participants	Baseline: 1309 eligible families, of whom 667 (51%) completed the pretest; Age: 6th graders, age 11 Gender: 55% F Ethnicity: no data Baseline smoking data (Wave 1): log‐transformed index of tobacco use: control (n = 129) 0.05 (SD 0.21), PDFY (n = 122) 0.13 (SD 0.34), ISFP (n = 122) 0.08 (SD 0.28)
Interventions	Category: social competence vs. social competence vs. control Programme deliverer: project staff Intervention: The 7‐session (ISFP) used concurrent 1 hr sessions for parents and children: parents were taught to clarify expectations; use appropriate discipline; manage strong emotions regarding their child; effectively communicate with their child; and the children's sessions paralleled the parents' sessions and also included peer resistance and peer relationship skills training; during family sessions family members practiced conflict resolution and communication skills and engaged in activities to increase family cohesiveness and positive involvement of the child in the family; The 5‐session (PDFY), which hypothesizes that bonding to prosocial others is a key protective factor against substance abuse, and that bonding with family members facilitates bonding with school and prosocial peers. 4 sessions were for parents only: parents were instructed on risk factors for substance abuse; developing clear guidelines on substance‐related behaviours; enhancing parent‐child bonding; monitoring compliance with their guidelines and providing appropriate consequences; managing anger and family conflict; and enhancing positive child involvement in family tasks; in 1 session children were instructed on peer resistance skills. Control: 4 mailed booklets (physical and emotional changes in adolescence; and parent‐child relationships).
Outcomes	(1) Ever smoked, (2) ever used chewing tobacco, (3) cigarettes per day, (4) no. of times chewed tobacco in the past month. All 4 measures dichotomised Yes = 1/No = 0, then summed from 0 to 4, then log transformed. Follow‐up: age 18
Notes	Quality of intervention delivery: (a) for the PDFY programme a process analysis showed that all teams covered all key concepts, and 69% of the detailed tasks in the group leaders' manual were completed. Of the attending families, 93% attended at least 4/5 sessions. The leaders covered all of the key concepts, and of the activities in the group leader's manual, 87% were covered in the family sessions, 83% in the parent sessions, and 89% in the youth sessions; (b) for the ISFP intervention, 94% of attending families were represented by 1 family member in 5 or more sessions, and observation of ISFP teams showed that all key programme concepts were covered; 373 families (56%) completed all 5 data assessments across 4yrs Statistical quality: Was a power computation performed? No Was an intention‐to‐treat analysis performed? Not stated Was a correction for clustering made? Yes Were appropriate statistical methods used? The groups were equivalent at baseline and multilevel analyses with logistic growth curve techniques controlled for the effects of clustering; multilevel mixed model ANCOVA; dichotomous outcomes by z tests
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"Schools were blocked on the proportion of students who resided in lower income households and on school size. Within blocks, each school was randomly assigned to one of the three experimental conditions... Random assignment was computer‐generated by a data‐analyst..." Clusters: schools Cluster constraint: blocked on the proportion of students who resided in lower income households and on school size Baseline comparability: no differences (Spoth 2001, Guyll 2004)
Allocation concealment (selection bias)	Low risk	No statement
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	No statement
Incomplete outcome data (attrition bias) All outcomes	Low risk	1,309 eligible families recruited, and 667 (51%) completed pretest. Although only 447 (67%) remained at 4 years, there was no differential attrition across groups; a multiple imputation Monte Carlo software programme (NORM) showed that attrition did not affect the findings; there was also no differential attrition after 6 years (Spoth 2004)
Selective reporting (reporting bias)	Low risk	No selective reporting