Parenting is an important rite of passage and can be challenging under even the best of circumstances. Parents with severe mental illness face additional challenges, such as increased risk of socioeconomic difficulty, marital discord, isolation and homelessness, impaired parent-child relationships, and children with mental illness and behavior problems. Parents with severe mental illness may also have concerns (rightly or wrongly) that their illness may jeopardize their custody or visitation rights with their children. There are no formal practice standards to assess parental mental health or parental fitness, and it has been suggested that some parents may lose custody or parental rights without an adequate assessment. The current academic literature, which is focused on mothers, indicates that the risk of losing child custody or parental rights may be as high as 60%. However, these studies are largely composed of mothers who are severely, chronically ill and impaired (and often psychotic); they are also limited to single programs or discrete regions within a state.
Your question on academic point of view though good but little is known regarding the clinical, functional, and quality-of-life effects on patients (mother / father) or their children of the fear of losing custody (either perceived or actual), despite the far-reaching effects it may have on a family.
However, in India the Indian Court unfortunately have not recognised these and are alien even to understand the methodology adopted for such assessment and directly flow with the opposing grounds more than what is "wise" for the point of view of "welfare of a child".
I will add, unfortunately I can't give very good answers to your raised question but personally speaking if the mother is undergoing treatment then I donot see issues in atleast a supervised visitation of her own child with her and actually your question can be better handled at SC level with lots of social and academic research materials assistance of a better Sr. Advocate on Record than at trial Court level whose Hon'ble Judges frown to the sight of an IA (Interlocutory Application) of a small unharming psyc. examination of other parent and or even that of a child during visitation / custody battles as they are not trained to understand its usage and impacts in making a "wise decision" by being a "wise parent" .