A Transdiagnostic Mentalization-based Intervention for Parents With Mental Disorders

Parenting stress assessed with Parenting Stress Index - Short Form (PSI-4-SF)

PSI-4-SF is a 36-item questionnaire assessing self-reported levels of parenting stress. The PSI-4-SF consists of three subscales: Parental Distress (PD), Parent-Child Dysfunctional Interaction (P-CDI), and Difficult Child (DC). A total stress score indicates the overall level of parenting stress as experienced by the parent. Parents rate the degree to which they agree with each statement (SA: Strongly agree, A: Agree, NS: Not sure; D: Disagree, SD: Strongly Disagree). Range: 36-180 with higher scores indicating higher levels of parenting stress.

Psychological adjustment in children assessed with the Strenght and Difficulties Questionnaire - Extended version (SDQ)

SDQ is a 25-item questionnaire assessing parent-reported child emotional and behavioural problems. The SDQ has five scales (scored 0-10); emotional problems, conduct problems, hyperactivity, peer problems and pro-social scale. The scales are combined (excluding the pro-social scale) into a 'total difficulties' score (Range: 0-40, with higher scores indicating more problems). The items on the overall distress and impairment can be summed to generate an impact score (Range: 0-10), indicating the need for assessment and possible intervention. Parents rate the degree to which they agree with each statement (NT: Not true, ST: Somewhat true, CT: Certainly true). Higher scores indicate more problems or more functional impairment.

Quality of life in parents assessed with the World Health Organization Questionnaire of Life - BREF (WHOQL-BREF)

WHOQL-BREF is a 26-item questionnaire assessing self-reported quality of life. The instrument measures an individual's overall quality of life and general health and four health dimensions: Physical health, psychological, social relationships, and environment. The domain scores are scaled in a positive direction with higher scores indicating a higher quality of life. The two domains assessing psychological health (6 items) and social relationsships (3-items) and the measure of the overall quality of life and general health (2 items) will be used.

Family functioning assessed with the McMaster Family Assessment Device - General Functioning Scale (FAD-GF).

The FAD is a questionnaire assessing self-reported perceptions of the parent's current family relationships. It consists of five subscales: problem solving, communication, roles, affective responsiveness, affective involvement, behavior control, and general functioning. Parents rate each statement on a 4-point scale (SA: Strongly agree, A: Agree, D: Disagree, SD: Strongly Disagree). Only the general functioning (6-items) subscale will be used.Range: 6-24, with higher scores indicating more functional impairment.

Childhood adversity in children assessed with the Adverse Child Experciences Questionnaire (ACE) extended version developed by the Center for Youth Wellness (CYW)

ACE CYW is questionnaire assessing parent-reported childhood adversity in children and adolescents. The instrument is comprised of two sections: Section 1 consists of the traditional ten ACEs covering exposure to childhood psychological, physical, and sexual abuse as well as household dysfunction, including domestic violence, substance use, and incarceration. Section 2 includes seven (CYW ACE-Q Child) or nine (CYW ACE-Q Teen) items assessing for exposure to additional early life stressors, including involvement in the Foster Care system, bullying, loss of parent or guardian due to death, deportation or migration, medical trauma, exposure to community violence, and discrimination. Parents are asked to how many categories apply to their child (i.e. they do not specificy which categories applies). Parents tally the number for each section, and report the total number, thus resulting in two total scores. Higher scores indicates exposure to more adverse events.

Parental mentalizing assessed with the Parental Reflective Functioning Questionnaire (PRFQ)

PRFQ is a 18-item questionnaire assessing self-reported parental mentalizing.Higher scores on the PM indicates impaired mentalizing, while high and low scores on IC and CMS indicates impaired mentalizing.

Mind-mindedness assessed with the Representational Mind-Mindedness (MM) interview

In the MM interview, parents are asked to describe their child. The response is taped and verbatim transcribed. The description is the coded following the guidelines from the coding manual (Meins \& Fernyhough, 2015). Total score range: 0-150, with higher scores indicating better mentalizing.

Epistemic trust assessed with the Epistemic Trust, Mistrust, and Credulity Ques-tionnaire (ETMCQ)

ETMCQ is a 18-item questionnaire assessing self-reported trust in others. Higher scores on trust indicates higher levels of trust, while higher scores on mistrust and credulity indicates epistemic mistrust.