This is a randomised controlled trial of an intervention to reduce symptoms of anxiety in the children of anxious parents. Parents will participate in an online intervention which helps them develop a calm, consistent, behaviour management style. The parents will be randomised to the intervention or a control group with no intervention. The intervention itself will undergo a component analysis to determine whether some modules are more effective than others.

The study is an online course (derived from an existing evidence-based face-to-face workshop designed and evaluated by the C.I) which aims to reduce symptoms of anxiety in the children of anxious parents. It is a learning tool to help parents to understand the basic processes involved in children's anxiety, to develop a calm, consistent, behaviour management style and to learn skills for responding to difficult emotion in their children.

The whole study takes place online, allowing the participants to sign up, run through some brief eligibility questions, read the study information and provide consent.

Once enrolled in the study, there is a series of baseline questionnaires. The participant also has the option to nominate someone who also knows their child well (e.g. a co-parent, a family member or close friend) to participate in the study with them and to complete a small number of questionnaires. This will help to give us a broader, more objective picture of the child, but is an optional part of the study. 48 hours later (to allow time for the participants to contact the co-respondent if they choose) the index participant will be randomised to one of two groups: either the intervention (the online course), or the control group where they do not receive the intervention.

Those in the intervention will be randomised to receive 8 out of 9 modules of the course, with a suggested time frame of one or two modules a week, each module taking about 30 minutes, with some home-practice tasks in-between.

Both the intervention group and the control group participants will be contacted again after 6 months to complete a set of follow-up questionnaires (similar to those completed at baseline). Depending on when each participant joins the trial, they may be contacted a third time towards the end of the life of the study, to complete another set of questionnaires,9-21 months after their first.

Inclusion Criteria:

• Be a parent (any gender, adoptive/biological/step/foster/grandparent) aged 16+, of a child aged 2 to 11 years (inclusive). The index parent must have at least 50 days' contact with the index child per year and confirm that they see enough of the child to report on the child's current anxiety level.
• Index parent must be a UK resident.
• Self-report subjectively substantial levels of current or lifetime anxiety.
• Able to commit to completion of measures at (up to) three time points even if allocated to the control arm.

Exclusion Criteria:

• N/A

Data will not be shared on an individual basis. Anonymised study data will be archived at the end of the study through the University of Sussex data repository, Figshare.