JUDGMENT K. Narayana Kurup, J. 1. Respondents 1 to 3 in the original petition are the appellants. The appeal is directed against the judgment of the learned Single Judge setting aside Ext. P3 and directing the appellants/respondents to grant disability pension to the petitioner. 2. The brief facts necessary for the disposal of the appeal areas follows: The petitioner/respondent was enrolled in the Army on 20-10-1984 and invalidated out of service on 5-4-1992 on account of I.D. - Affective Psychosis (Depression). Before boarding out he was treated in the military hospital and at the time of his discharge he had put in service of 7 years and 6 months. Though the petitioner/ respondent applied for disability pension the same was rejected by the authorities and against which the petitioner filed Ext. P2 appeal which was rejected by Ext. P3 order of the Union of India on the ground that the disability was due to constitutional disease of the petitioner/respondent and it did not develop due to stress and strain of military service. Aggrieved thereby the petitioner moved this court by the present writ petition out of which this writ appeal arises. 3. According to the petitioner/respondent, he was physically and mentally fit at the time of his recruitment and the development of the disease thereafter is clearly attributable to the military service and not due to any other reason. Per contra, it was contended by the appellants that the disability of the respondent/ petitioner is a constitutional disease unconnected with his military service disentitling him to disability pension. The learned single Judge, however, accepted the argument of the respondent/petitioner and quashed Ext. P3 holding that the illness could be attributable to military service. Hence this appeal. 4. Having heard learned counsel on both sides we are of the opinion that the reasoning of the learned single Judge while granting relief to the petitioner/ respondent cannot be legally sustained. The learned single Judge, however, accepted the argument of the respondent/petitioner and quashed Ext. P3 holding that the illness could be attributable to military service. Hence this appeal. 4. Having heard learned counsel on both sides we are of the opinion that the reasoning of the learned single Judge while granting relief to the petitioner/ respondent cannot be legally sustained. It appears that the learned single Judge was persuaded to grant relief to the petitioner on the premise that the petitioner who was mentally fit at the time when he joined service in 1984 got mentally sick by virtue of the fact that "he was working at a distant place away from home." According to learned single Judge, the illness of the respondent/petitioner may be due to the condition under which he was working or due to various other circumstances under which he was working." We are afraid, we cannot subscribe to the aforesaid view of the learned single Judge. Had it been the case of the respondent/petitioner that his affliction could be specifically attributable to or aggravated by military service we would have been inclined to take a lenient view. On the contrary, what we find is that the disability on account of which the respondent/petitioner was invalidated out of service is a constitutional disease. The appellate medical authority has found that onset of ID - Affective Psychosis (Depression) was in October 1990 while serving in a peace area. It has also been found that there is no evidence of undue stress and strain due to service prior to onset of ID. Therefore, the authorities cannot be faulted in treating the disability of the respondent/petitioner as neither attributable to nor aggravated by duties of military service. Once the expert body like the Medical Board expresses an opinion it is entitled to great weight. Unless the medical findings are utterly perverse this court exercising jurisdiction under Art.226 of the Constitution cannot go behind the said opinion and substitute its own opinion for that of the expert body. There is no material before this court, much less medical, to hold that the disability of the respondent/petitioner is attributable to or aggravated by duties of military service. There is no material before this court, much less medical, to hold that the disability of the respondent/petitioner is attributable to or aggravated by duties of military service. On the contrary, we find that the origin of affective disorder (depression) is a genetic and of biological predisposition with psycho social factors playing a contributory role, neither of which has any casual connection with military service. Reported studies are most consistent with the hypothesis that mood disorders are associated with heterogeneous dysregulations of the biogenic amines. (Synopsis of Psychratry by Harold I. Kaplan and Benjamin J. Sadock, Eighth Edition, Pages 524 & 539). At the risk of repetition we would observe that the . respondent/petitioner was not working in any forward area/battle front and that the nature of the work also did not involve any stress and strain triggering a psychiatric event. Therefore, it will be reasonable to hold that he will not be entitled to disability pension as the disease was genetic, biological and constitutional in nature and the disability was neither attributable to nor aggravated by the stress and strain in the military service. That apart, the disability has been assessed by a competent expert body like the medical board whose conclusions are to be accepted as correct unless contradicted by any other medical board by cogent evidence. It appears that this aspect of the matter was lost sight of by the learned single Judge while ordering disability pension to the respondent/petitioner. In the absence of any material evidence, the learned single Judge was not justified in interfering with the findings based on the opinion of the Medical Board. This court while exercising jurisdiction under Art.226 of the Constitution is not sitting as an Appellate Court. The findings of the expert body cannot be interfered with unless it is palpably wrong. During the total service of the respondent/petitioner he has never been posted to border areas or areas having adverse climatic conditions. His nature of work cannot involve any such risk. Taking into account all these facts we are of the opinion that the learned single Judge was not justified in holding that the illness could be attributable to or aggravated by military service. 5. In the result, we set aside the judgment of the learned single Judge and allow this Writ Appeal and dismiss the original Petition .