In this randomized control study, investigators will evaluate the effectiveness of the Acceptance and Commitment Therapy (ACT) matrix behavioral protocol compared to Parent Training (PT) programs in improving the psychological well-being of parents of children with Autism Spectrum Disorder (ASD). Twelve parents will be randomly and equitably assigned to two matched groups in which individuals will undergo 24 weekly ACT (experimental group) or conventional PT (control group) protocol meetings

Autism Spectrum Disorder (ASD) is a lifelong neurodevelopmental disorder characterized by core deficits in maladaptive behaviors, communication skills, and self-regulation im-pairments affecting the socio-relational performance of children, but also of their parents. It has widely been demonstrated that raising a child with autism involves chronic challenges consistently associated with high levels of psychological distress. Often parents become isolated from family and friends who may not understand the child's be-havior and disability. The chronic stress experienced by parents of children with ASD also reported to be greater than those experienced by parents of children with other disabilities, such as Down Syndrome, behavioral disorders and Fragile X Syndrome, and also associated with increased divorce rates.

It is clear that family members, in this condition, should be supported in the development of new parenting skills useful to achieve targets of intervention while reducing psycho-logical distress. Indeed, reinforcement of parental resources has been considered as potential mediating factors of ASD treatment, which may reduce maladaptive behaviors in children. The present single-blind Randomized Controlled Trial (RCT) is aimed to compare, for the first time, the efficacy of the ACT approach in ASD parents with respect to the PT. Several papers reported the beneficial effects of PT groups as classic support to increase parenting skills in managing the behavior of children with ASD while reducing parental stress. Nevertheless, none has evalu-ated if ACT may be a more powerful approach to threat psychological reaction to the stress of caring for ASD children. The investigators hypothesized that psychological difficulties of parents of children with autism could decrease after a course with goals of transmitting behavioral educational techniques and promoting psychological adjustment through defusion and acceptance strategies. Primary outcome measures and secondary outcome measures will be collected. A pre/post-treatment assessment will be conducted regarding the measurement and change in parental psychological flexibility during the intervention. The primary outcome measures that will be used are the Acceptance and Action Questionnaire II (AAQ-II) to measure the person's psychological flexibility and ability to stay in touch with emotions and the Home Situation Questionnaire (HSQ-ASD) which give objective measures of the perception and influence of children's behavior in the parents' lives. Secondary outcome measures will be the Valued Living Questionnaire (VLQ) to identify areas important to the person, the Mindfulness Attention Awareness Scale (MAAS) which measures an individual's tendency toward intentional awareness, and the Parental Stress Index (PSI) to assess pre- and post-treatment stress levels.

The families were recruited as part of an ongoing research program and tested at our clinical facilities.

Inclusion criteria were based on children characteristics as follows:

• between 3 and 13 years of age;
• clinical diagnosis of ASD based on the DSM-5 criteria from a licensed clinical child neuropsychiatrist;
• DSM-5 severity scores from mild (level 1) to moderate (level 2) in both social communication and restricted interests and repetitive behaviors domains;
• a verbal and performance Developmental Quotient: Griffiths Mental Development Scales, Extended Revised: 2 to 8 years (GMDS-ER 2-8 Luiz et al. 2006) and Wechsler Intelligence Scale for Children (WISC-IV Wechsler D. 2003) above 70;
• no hearing, visual, or physical disabilities that would prevent participation in the intervention;
• not being on psychiatric medication. All children have a previous diagnosis that was further confirmed through the assessment and the consensus of experienced professionals on the research team (i.e., a child neuropsychiatrist and a clinical psychologist).

The following people were all blinded to the group membership of the parents: the physicians (who carried out the clinical baseline assessment [T0] and post-treatment investigation [T1]), the primary researchers, and the data entry assistants. In the fourth stage, participants underwent ACT or PT training therapies. Treatments were carried on by expert therapists who were blinded to all clinical information and also to the aim of the study. At the end of treatment, participants from both groups were given a final evaluation [T1], using the same protocol as at a baseline.