Received structured eight-week psychosocial sessions

Controls wait-listed for the intervention, matched for age and urban residence

The "Advancing Adolescents" programme is a structured 8-week psychosocial intervention for adolescents in humanitarian crises, based on profound stress attunement processes. It features three elements that are widely viewed as important to support youth adjustment in contexts of complex emergencies: (i) safety: establishment of a 'safe space' within the community as a base for activities and site of protection; (ii) support: facilitation of social support and self-expression; and (iii) structured activities: access to scheduled group activities.

Insecurity was measured with The Human Insecurity (HI). This tool was developed for use in the West Bank (Ziadni, Hammoudeh et al. 2011, Hamayel, Ghandour et al. 2014). The 10-item scale is a 5-point Likert scale with scores expressed as percentages on a scale of 0-100. The HI covers issues such as worries regarding inability to obtain daily life necessities, losing a source of income, fears about the future, and family safety.

Distress was measured with the Human Distress scale (Hamayel & Ghandour, 2014), developed for use with conflict-affected adolescents in the West Bank. The 12-item scale is a 5-point Likert scale with scores expressed as percentages on a scale of 0-100. Sample items include, "To what extent have you felt worried," "To what extent did you feel humiliated," and "To what extent did you feel angry." Scores are presented as percentages (0-100%), with higher scores indicating greater distress.

Stress was measured using the Arabic version of the Perceived Stress Scale (Cohen, Karmarck, & Mermelstein, 1983), validated with a Jordanian sample (Almadi, Cathers, Hamdan Mansour, & Chow, 2012). This 14-item, 5-point Likert scale measures perceived stress over the last month, with higher scores indicating greater stress. Items include, "How often have you been upset because of something that happened unexpectedly?" and "How often have you been able to control irritations in your life?" (reverse-scored) (1 = Never, 5 = Very often).

Mental health was assessed using the 21-item Arab Youth Mental Health questionnaire (Mahfoud et al., 2011; Mahkoul et al., 2011). This measure includes questions such as, "During the last week I was upset", "During the last week I was bored and hated my life", and "During the last week, I was having a lot of headaches, stomach-aches, and nausea" (1 = Rarely, 3 = Always). Higher scores indicate more symptoms of anxiety and depression.

The Arabic version of the Child Revised Impact of Events Scale (CRIES-8, 4-point scale) was implemented to assess posttraumatic stress symptoms. Analysis will be on dimensional scores, noting that CRIES >17 points is predictive of symptoms of posttraumatic stress disorder (http://www.childrenandwar.org).