Internal Audit has a role to play when it comes to mental health! It starts with ensuring that its own staff are enjoying good mental health.
Internal Audit can play a vital role in helping the organization promote and improve mental wellness and provide assurance on the effectiveness of the organization's policies and practices and provide insight that can help improve them.
More details are discussed is an older post:
My Thoughts: Internal Audit and Mental Health! (waelbibi.blogspot.com)