I am doing a bit of family history - one ancestor was in and out of lunatic asylums in London, but it is never stated what condition he had? He 'recovered' a few times though. Thank you.
Do you have any more information about this individual? Because it could have been for just about any reason. Asylums even up into the mid to late 20th century were often used to hide away "problem" individuals, rather than offer actual treatment (though some did the best they could). This could range from serious mental illness to physical or developmental disabilities to just plain disobedience of your spouse, parents, or the law. If it was a mental illness, it was painted with a much broader brush than mental illnesses are today, and many conditions that we now view as separate would be viewed as the same thing, often with a different name than we use today.
What age were they when they were committed? Was it during childhood and adolescence, or did it continue while they were an adult?
In Ireland (which was under English control during this time period), the asylums were a part of a wide web of institutions designed to catch members of society from falling into destitution. Workhouses, gaols (jails), reformatories, industrial schools, mother and baby homes, magdalene laundries, and lunatic asylums were all connected in that people entered them out of force or desperation and many inmates of one institution were moved to another for a variety of reasons. The Dangerous Lunatics Act allowed for the forcible confinement of anyone perceived to be a threat into the gaols or the lunatic asylums. From the records that I've looked at it shows people's admittance to the lunatic asylums as being either due to "mania," "melancholia," criminal lunatic," "simple idiocy," "epilepsy," "hysteria," and "delerium tremens." It was vague and the ages ranged from small children to the elderly. The people that were often moved into the asylums were most likely a burden to the workhouse or other institutions housing them.
I've heard of examples of women that were confined by their family members to the more upper-class private asylums with evidence that this was due to arguments over rights to property and family inheritance as well but I have not personally seen any examples of this.