British India - Mental Illness was more prevalent in hilly regions, not much in plains

Summary

1. Hills had higher insane. Plains had much lower insane 
- within Assam, Lushai Hills reported a rate 8 times more than the plains
- Mysore had much higher than neighboring Madras state (Mysore is a hilly region)
- Burma had one of the highest insane (Burma has lot of hills)

2. The number of insane in UK was 12-14 times than in India 

1871

The very first attempt to estimate the number of mentally ill in India and the differences in rates of insanity was made in the census of 1871.[1] The census of 1871 was also the first time that estimation of the number of “imbecile, idiot or lunatic” was attempted in the UK itself, and the India data thus offered a useful counterpoise. The number of insane and idiots in India was estimated at 67,000 (1 in 2700), a proportion which was one-eighth that of England and Wales (where the total number of lunatics was estimated as 39,567 of whom 35,790 were in Asylums, in a population of 22.7 million).[2] Absence of over work, over excitement, and low rates of intoxication in India were thought to be one reason for these low rates, while it was also suggested that a chronic starvation perhaps did not supply enough nutrition to the brain (to allow the furor of insanity to occur). Differences between Europe and India were also being observed clinically by then. Commenting on the trends in outcomes for admissions into the Bengal asylums (1848–1870), in the Indian Medical Gazette,[3] it was noted that the proportion of admissions who recovered (55–63%) was higher than in England (34%) and Victoria, Australia (49%). It was suggested that the better outcome was a reflection of the fact that most admissions were for those who were recently ill and the numbers of chronic residual ill were rather small. Death rates were also high, so the outcome for patients was either recovery or death (30–36%, as compared to 20–30% in England and Australia). The census thus detected lower incidence and a background of better recovery for mental illness in India. Within India, Mysore region was reported to have a higher rate of insanity than the adjoining Madras. Some reasons (psycho-social and biological) for these differences were suggested.

1881

By the time of the next census in 1881,[4] serious concerns were already in place about the errors in enumeration caused by inadequately trained field staff. This was particularly worrying as the rates detected (35/100,000) were a fraction of those in Europe (which varied from 130/100,000 in England to 38/100,000 in Sweden). Sweden and northern Europe were at that point in time considered underdeveloped and poor, and thus closer to the social situation in India. Even more surprisingly, there were inexplicable differences within India, with Burma recording 100/100,000 while Cochin and North West Frontier had 17/100,000. These differences were examined for the influence of age, gender, geography, religious factors, and interactions between these. No consistent pattern emerged, so it was assumed that the variations were caused by errors in enumeration. Specifically, it was thought that those with milder forms or periodical insanity (and were currently normal) had not been counted at all.

The census of Mysore (being an independent territory) was done separately.[5] The initial count of 1871 had found that Mysore had a higher rate of insanity that many other parts of India, which prompted a specific question from the Government regarding the possible reasons for this, and the census of 1881 tried to answer these. Dr. Houston and Dr. Henderson, from the Asylum in Bangalore (now NIMHANS), who had lived in Mysore for many years, said they could not think of any possible reason for the higher rate of insanity in terms of geography or temperament. However, the Census Officer (Mr. B. L. Rice) speculated that consanguinity, social breakdown, and the large and rapid demographic changes in Bangalore caused by migrations from Maratha, Hyderabad, Madras, and Malabar regions (over the previous two centuries on account of the various Anglo-Mysore Wars and the British occupation) had given rise to a very “vagrant and bohemian” lifestyle that could account for this increased prevalence of abnormal behavior, that could be linked to the higher prevalence of insanity in Mysore.

1901

The effects of race and religion (compulsory data points) and caste (an optional data point) on prevalence of insanity were documented. Differences between the Mongoloid and Dravidian groups, and of particular clusters within these broad groupings, were detected. Prevalence by ethnic, religious and caste groupings suggested that the prevalence declined gradually, being the highest in Eurasian and Parsees, followed by Muhammadans, and within the Hindus, “the liability to insanity varies roughly with social position - the highest castes suffer most and the lowest castes least of all.”

1911

These records (8) extended observations in more detail. Though the prevalence of insanity had increased by 9% since the previous census, it was still 14 times less than in England and Wales. As earlier, highest rates were reported from the fringes of the empire (Burma and the north-west), but local variations were also high (within Assam, Lushai Hills reported a rate 8 times more than the plains).

The variations based on caste were not thought to be useful at all, as within the Brahmins, there were regional differences even within southern India, with prevalence declining in order from Malayali, Canarese, Telugu, and Tamil Brahmins.




https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3339215/