Consent Needed for Treatment of Psychiatric Patients?
Treating a patient without his/her knowledge or treating forcibly is unethical. Also there could be chances that someone takes advantage of this and there could be many loopholes.
However in movies like "Bhool Bhulaiya" it's shown happening.
As you said it depends on the condition of the patient; whether he/she is capable enough to take decision on his/her behalf plays vital role here. If someone is capable of harming him/herself or others under mental-illness then the family may take decision of treatment on his/her behalf. Again this has to be decided by the medical laws.
As Sanchi tried suicide and caused havoc in Singh as well as Sekhar's lives it cannot be considered as a personal decision. If not treated she may harm more people.
If I remember correctly even the judge had advised Sekhars to get her treated for her mental illness.
Here is an interesting medical article on this theme https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3031933/
Here are some information from this article.
Who takes the decision? - Need for a substitute decision-maker
Person incapable of consenting to treatment, a substitute decision-maker (SDM) interested in his/her welfare will make a treatment decision on his behalf. In this process one needs to take into account his wishes before he was found incapable.
Factors to be considered for an informed decision by SDM-
1.1.Nature of the treatment: what it is and what it involves
2.2. Expected benefits of the treatment
3.3. Potential or likely risks of the treatment
4.4. Potential or likely side-effects of the treatment
5.5. Other treatments or therapies that may be available
6.6. What could happen to the patient if the treatment is not given
There are, however, many instances in which medication is given without consent, covertly or otherwise, in all vulnerable patient populations whose "best" interests are being decided by a variety of surrogates.
Medical laws are still not very strong in India as they are in west. They are still in formation