First, I am not a mental health or addiction professional. I cannot and do not make diagnoses or offer treatment for any medical condition or addiction. However, allegations of mental illness and addiction are often made in the family courts and I have to deal with those allegations, both by making them and defending people against them. Below I set forth my observations; your mileage may vary and I highly recommend seeking qualified counsel if you are involved in a child custody case with allegations of mental health or addiction issues.
A mentally ill or substance-dependent parent will have difficulty obtaining sole custody or joint custody of their children in a contested proceeding as compared to an otherwise equivalent non-mentally ill or addicted parent. The court, remember, is obligated to determine child custody by employing the best interest of the children standard and relatively small differences can have a great impact. How difficult a case for such a parent will be depends on how parent actually behaves. Having the blues after a relative has died or drinking a beer after dinner before bed every night is not a substantial impediment to caring for your children while hallucinations, threatened suicide or homicide, or a meth addiction are quite worrying to any reasonable judge (and your local child protection agency).
In the best of scenarios, a parent seeking custody is not mentally ill or substance-dependent at all. Unfortunately, life doesn't work that way; people frequently are afflicted with mental illness or have succumbed to addictions, need help to overcome it, and have children, too.
If you are fighting with the other parent or a guardian (or grandparents or DHS or whoever) for custody of your children and you are alleged to be a person in need of treatment, then you should probably seek it. If the allegation is false or is greatly overstated, then your counselor or therapist can come testify to that fact or offer a report to the court and/or the guardian ad litem and thereby undermine an important part of the argument against you. If a professional concurs that you do need treatment, you can obtain the treatment and undermine an important part of the argument against you since you have or are resolving the issue. Addressing such allegations is always important for your case.
Generally, in my experience with family court, if you are, in fact, mentally ill, everybody who's going to testify will be confronted with and asked to explain and comment on the evidence of your mental illness or addiction. Under cross-examination, they will admit to those elements of your behavior and to past incidents that reinforce that negative narrative, even your sister, your best friend, and your mother. Your attorney will attempt to rehabilitate you in the eyes of the court by getting them to “explain away” the behavior in a way that doesn't undermine your case, but it won't be as effective as you want because the objective facts are damning and, even worse, unaddressed by you, while the “explaining away” is self-serving.
Lots of your past behavior, behavior that seems reasonable to you and which you can explain to your own satisfaction and that of your close friends, and which may actually even be reasonable, can be cast in a way that will illustrate your relative unfitness for custody even if the behavior or incident is actually unrelated to any mental illness or addiction. We live in a world of smart phones. They're everywhere and there is usually an audio recording (usually a message left on a phone, but very often a video) of you saying something that sounds mentally ill or threatening or even just incoherent, and the judge will hear that, and your denials will generally be ineffective since your even your mom will be forced to admit to your crazy behavior.
However, all is not lost. There is hope in addressing the problems head-on. Court cases are all about evidence and competing narratives. Overcoming mental illness or adiction by taking responsible action actually creates a useful narrative for your custody battle. If you have a problem and you've obtained the help you needed, you have by those acts demonstrated to all observers including your judge that you have the character needed to continue to parent your children. Not only is there a narrative, though, drug and mental health treatment produce documentary evidence which can be submitted to the court for it to review. In addition, the testimony of the counselor you sought out when you were confronted or accused of mental illness will generally be very credible and sympathetic.
The alternative narrative, if a person with problems fails to correct them, is that of the unstable person who is in denial and refuses to get help. Which person would you rather have raising your children? Would it be in the best interests of your children to leave in the care and custody of such a person? This is the sort of thing a judge has to decide when confronted with allegations of mental illness and addiction when they are required to make a custody decision. How to dispel this kind of narrative is something you have to consider if you're fighting over custody.
If you need help for this kind of problem you should get it. It will help you and it will help your kids. If you're clearly not mentally ill, but you've been accused then get it documented so you can turn the tables. If mental illness or addiction is an issue in your child custody or divorce case call a divorce lawyer at (405) 310-9890 for a free consultation.