8886[.019] F – Statistics 8

Normal cobalamin Concentration

Cobalamin deficiency (<200pg/ml)

41 (77.7)

12 (22.6)

205 (89.1)

25 (10.9)

246 (86.9)

37 (13.1)

Total (%) 53 (100) 230 (100) 283 (100) 0.022

Normal folate Concentration

Folate deficiency (<3ng/ml)

51 (96.2)

2 (3.8)

223 (97)

7 (3)

274 (96.8)

9 (3.2)

Total n (%) 53 (100) 230 (100) 283 (100) 0.785

Normal homocysteine Concentration

Hyperhomocystinemia (>15µmol/l)

32 (60.4)

21 (39.6)

149 (64.8)

81 (35.2)

181 (64.0)

102 (36.0)

Total n (%) 53 (100) 230 (100) 283 (100) 0.547

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DURATION OF PSYCHIATRIC ILLNESS AND LEVELS OF BIOCHEMICAL PARAMETERS

There was no correlation between duration of psychiatric illness and levels of homocysteine, folate and cobalamin. (p > 0.05 in all three biochemical parameters). Table 11.

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TABLE 11: DURATION OF PSYCHIATRIC ILLNESS WITH LEVELS OF BIOCHEMICAL PARAMETERS

Variable Pearson Correlation Coefficient (r)

P-value

Homocysteine -0.002 0.974

Folate 0.064 0.334

Cobalamin -0.125 0.059

80 CHAPTER 6 DISCUSSION

This study was carried out among individuals with psychiatric disorders attending the outpatient clinics of the two foremost health institutions in Lagos namely Lagos University Teaching Hospital and the Federal Neuropsychiatric Hospital Yaba. The main goals of the study were to determine the prevalence of cobalamin and folate deficiencies as well as hyperhomocysteinemia in individuals with psychiatric disorders, to classify individuals with psychiatric disorders according to WHO’S tenth revision of the International classification of diseases¹⁷ and to determine if any of the mental disorders elicited was associated with cobalamin, folate and homocysteine derangements.

Psychiatric disorder is of major concern worldwide with majority of people afflicted living in developing countries.¹The prevalence rate of psychiatric disorders in Nigeria is approximately 20% of the population.⁴ This level of disease burden in our environment could be as a result of decreased intake of meals rich in cobalamin and folate needed for proper functioning of the brain.

In the present study, the mean serum cobalamin levels in psychiatric patient group (m± SD = 388.87±211.55pg/ml) were significantly lower compared with the control group (m±SD = 445.53± 197.96pg/ml) p=0.03. This finding was supported by a study done in Sudan which showed a significantly lower mean serum cobalamin in patients with psychiatric disorders (m ± SD = 527.9 ±305.8pg/ml) compared with the control group (m ± SD

=590.5±186.1pg/ml) p=0.001.¹¹⁶

A significant association was seen between cobalamin lack and patients with psychiatric illnesses (p= 0.005). This is similar to the study carried out in Sudan by Ezeldine et al.¹¹⁶The link between deficiency of cobalamin and a range of psychiatric disorders has been

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established in one study.¹¹ Result obtained from our study has further augmented the fact that an association truly exists between cobalamin lack and psychiatric illnesses.

Finding from this study is at variance with that reported by Bazuaye in 2003 where he found no association between cobalamin lack and psychiatric illness.¹² This is possibly due to the fact that the methods of cobalamin assays were different. Bazuaye used urine methylmalonate as a surrogate marker of vitamin B12 (cobalamin) levels while this study directly assayed vitamin B12 (cobalamin) by conventional ELISA technique.

Documented reports have shown that psychiatric manifestations accompany 4-50% of patients with cobalamin deficiency.⁷⁴ Locally, the prevalence of cobalamin deficiency in patients with psychiatric disorders in Nigeria still remains unknown.

In this present study, we found out that 20.4% of patients with psychiatric illnesses were deficient in cobalamin which is quite high. The prevalence rate was comparable to research works carried out in Israel and Uganda where the prevalence rate of cobalamin deficiency in patients with psychiatric disorders accounted for 12.6% and 28.6% respectively.^118,119

Although these high rates were attributed to genetic differences and decreased dietary intake, this cannot be directly inferred in our study since the level of cobalamin was not taken before onset of illness in a longitudinal study.

At present there is no worldwide consensus to the normal reference limit of serum cobalamin concentrations as reports have shown occurrences of neuropsychiatric abnormalities in patients with serum levels of cobalamin less than 300pg/ml. This observation has led health professionals to come to an agreement that the lower reference limit of serum cobalamin concentrations should be set between 300 and 350pg/ml.^120,121

Majority of patients in the study had schizophrenia (64.9%) and mood disorders (32.1%), while mental retardation (1.3%), anxiety disorder (0.9%), behavioural disorder (0.4%) and somatiform disorder (0.4%) made up the minority. The Biochemical parameters of patients

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with schizophrenia and mood disorders (depression and bipolar affective disorder) were evaluated because of their larger sample size which allowed for easy comparison as well as make valid inferences.

In this current study, there was significant association between cobalamin deficiency and Schizophrenia (p= 0.005). This finding was similar to research works carried out by authors in Israel and Uganda which showed low cobalamin levels in hospitalized patients with psychiatric disorders.^119,122

On the contrary, some authors found that mean serum cobalamin concentrations in schizophrenics were higher than healthy controls.^123,124 In our study, the mean serum levels of cobalamin in schizophrenic patients was significantly lower (378.2± 205.7 pg/ml) than the healthy controls (445.5± 198.0 pg/ml). p= 0.006.

The high prevalence of cobalamin lack in the subgroup of patients with schizophrenia may be explained by illness related factors that include poor appetite and inadequate dietary intake.

In this study, there was a significant difference in proportion of patients with cobalamin deficiency between depression and control. (p= 0.022). This finding was similar to research works carried out by authors in Rotterdam and Baltimore which showed low cobalamin levels in patients with depression.^91,101

Our study is at variance with a study done in Hordaland, Norway which showed no association between depression and cobalamin deficiency.⁸ This current study, however shows the mean serum levels of cobalamin in patients with depression was significantly lower (379±212.2pg/ml) than the healthy controls (445.5±198.0pg/ml). p= 0.006.

This finding is comparable to research works carried out by Ebesunum and colleagues in Nigeria, which showed significantly lower mean serum levels of cobalamin in depressed patients (38.07±7.62µg/dl) compared to healthy controls (46.09±5.7662µg/dl). p=<0.001.¹²⁵

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No assertion could be made as to whether the observed association with cobalamin lack was the cause or consequence of depression. The high prevalence of cobalamin lack in the subgroup of patients with depression in our environment may be explained by illness related factor that include poor dietary intake (due to loss of appetite). Consequently, cobalamin deficiency may further impair mental health of patients with depression by altering several metabolic reactions that mediate proper functioning of the brain.

In our study, the serum level of cobalamin was higher in patients with bipolar affective disorder compared to healthy controls.

Our study is at variance with a study carried out by Ozbek et al in 2008 were they showed cobalamin level was significantly lower in bipolar affective disorder patients with methylene tetrahydrfolate reductase gene mutation.¹¹²

The apparent lack of association between cobalamin deficiency and bipolar affective disorder might be a false negative finding since it is known that binding protein concentrations of cobalamin and immunoassay kits used may capture the inactive forms of cobalamin and cover true tissue deficiencies of active cobalamin.¹²⁶

There is a dearth of literature showing the prevalence of hyperhomocystinemia in patients with psychiatric illnesses in Nigeria.

In this study we found out that 45.2% of patients with psychiatric disorder had high homocysteine levels. This finding is in agreement with a study done in Tunisia which showed that hyperhomocystinemia was present in 34.4% of psychiatric patients.¹²⁷

The high prevalence rate of hyperhomocystinemia in our study could be as a consequence of genetic differences. Since it was discovered that the relationship between hyperhomocystinemia and psychiatric illness could be due to a defect in 5,10-methylene tetrahydrofolate reductase which helps in the remethylation of homocysteine to methionine.

Pathological accumulation of homocysteine could alter monoamines which subsequently

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impairs neurotransmitter production. Altered production of neurotransmitters can lead to adverse effects such as neuropsychiatric manifestations.^92,96,108

The study carried out by us, also showed a significant association between hyperhomocystinemia and schizophrenic group compared to the control group. (p= 0.008).

This is similar to a study carried out in India by Sunil K.N and colleagues.¹²⁸ Several other authors also found similar findings in their studies^{10, 108}

The conclusion was made by authors that elevated homocysteine level is a more common finding in newly diagnosed patients with schizophrenia^109,110 In our study, the prevalence of hyperhomocystinemia in schizophrenic patients was 49%.

Homocysteine which is a sulfur containing amino acid is mainly metabolized by two major metabolic pathways namely remethylation and transsulfuration pathways. In the remethylation reaction homocysteine is catabolised to methionine which is further broken down to s-adenosyl methionine (SAM). SAM is a universal methyl donor for numerous methylation reaction required for production of neurotransmitters, phospholipids, DNA and proteins.⁸⁶

In the brain, remethylation pathway is the only metabolic pathway for catabolism of homocysteine. This remethylation reaction of homocysteine with formation of SAM can only become possible in the presence of cobalamin. This cobalamin acts as a cofactor for the methionine synthase.

In this study, about a quarter of our schizophrenic patients with hyperhomocystinemia have cobalamin deficiency. This possibly means that methionine synthase enzyme might have been rendered ineffective due to lack of its cofactor cobalamin necessary for this reaction to proceed.

The consequence of this remethylation pathway shutdown is the pathological accumulation of homocysteine which can have several detrimental effects on the brain. These are neuronal

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DNA damage and apoptosis, distortion of neurotransmitters, reduction of methylation reactions and production of reactive oxygen species.^68,92

All these detrimental effects of pathological homocysteine accumulations can induce mental symptomatology in our patients with schizophrenia.

The study carried out by us, showed no significant association in homocysteine derangement between patient with depression and the control group. (p=0.547). Few other authors have shown similar findings in their studies.101,129,130

Majority of other authors however showed that a significant association exists between hyperhomocystinemia and depression.8,9,125,128,131

There is lack of significant association between homocysteine derangement and our depressed patients. These patients who were enrolled in our study with depression and who were found to be strongly lacking in cobalamin may show poor homocysteine sensitivity to tissue cobalamin deficiency. There are other metabolites such as methylmalonic acid which can be used to assess our depressed patients with cobalamin deficiency. Methylmalonic acid has a higher sensitivity for tissue cobalamin deficiency than homocysteine.

Our study showed no significant association in proportion of patients with hyperhomocysteinemia between bipolar affective disorder and healthy controls. p= 0.792.

Our study is at variance with that of other studies were they found significant association between hyperhomocystinemia and bipolar affective disorder.112,113,114

In the study carried out by us, there was no significant association between folate deficiency and psychiatric illnesses. p= 0.793. The serum level of folate was slightly higher in the psychiatric patient group (m±SD = 10.41±6.11ng/ml) than in the control group (m±SD = 9.93±5.32ng/ml). This finding is comparable with research works carried out by other health professionals in America, Sudan and Germany who were unable to demonstrate any

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significant difference in folate levels between patients with different psychiatric disorders and healthy controls.101,116,132

Our study is at variance with a study carried out in America were an association between patients with psychiatric disorders and low folate levels was shown.¹⁸

The lack of association between folate deficiency and psychiatric illnesses in our study and the slightly higher mean serum folate levels in psychiatric patients compared to controls, may be a consequence of the high prevalence of cobalamin deficiency in our patients.

The normal to slightly high folate levels seen in majority of our psychiatric patients with cobalamin deficiency may have a connection to the methyl folate trap hypothesis. This hypothesis is based on the fact that folate-requiring enzyme, methionine synthase is dependent on cobalamin.

Therefore, deficiency of cobalamin may have a detrimental effect on this enzymatic pathway leading to accumulation of 5-methyl tetrahydrofolate, the major form of folate in the serum.

In this study, our findings showed no reduced level of folate in patients with depression (p=0.785). Our finding is in agreement with other authors were they showed no association between folate lack and depression.^91,101,132

Our study is at variance with similar studies carried out by some other authors were they found a significant association occurred in the proportion of patients with folate lack between depression and healthy controls.^9,21,86In this study, the mean serum folate level in patients with depressive illness (11.5±5.6 ng/ml) is higher than the mean serum folate level in healthy controls (9.9±5.3 ng/ml).

In the current study, our finding revealed absence of a significant association between folate lack and schizophrenic patients (p=0.865). This finding is similar to the study carried out by Haidemenous A and colleagues.¹⁰⁹ Our finding is however at variance with a study by

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another author who found a significant association between folate deficiency in patients with schizophrenia.¹³³

This study, shows that the mean serum folate level in patients with schizophrenia (10.0±6.1 ng/ml) is comparable to the mean serum folate level in healthy controls (9.9±5.3 ng/ml).

This study also found no significant association between folate lack and bipolar affective disorder. This is contrary to one other study which showed a significant association.¹¹²

The normal folate level seen might be a sign of improved well-being following treatment.

There was no correlation between duration of psychiatric illness and levels of folate and cobalamin in our study. (p > 0.05 in all three biochemical parameters).

The mean haemoglobin level in control group (14.38±1.40) shows there was a significant difference when compared with the mean haemoglobin level in psychiatric patients (12.17±1.70). p=0.000. However, despite the statistical difference the mean haemoglobin in psychiatric patients are within the normal reference range for both male and female. This finding is similar to one study carried out in Sudan which showed a significantly lower mean haemoglobin level in psychiatric patients (13.2± 1.7) compared with the control group (14.1± 1.4). p = 0.000 ¹¹⁶

The red cell indices (MCV, MCH and MCHC) in psychiatric patients and healthy controls were within normal reference limits. Hence, no haematological manifestations (namely anaemia and macrocytosis) were found in the psychiatric patient group.

This finding is comparable to a study done by Vladimir et al¹³⁴ which showed no evidence of anaemia or macrocytosis despite significantly lower levels of cobalamin and folate.

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CHAPTER SEVEN CONCLUSION

This study has demonstrated that cobalamin deficiency and hyperhomocystinemia are prevalent amongst patients with psychiatric disorders.

Pathological accumulation of homocysteine secondary to B vitamin deficiency could possibly lead to further deterioration of mental health status in patients with psychiatric disorders.

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CHAPTER EIGHT RECOMMENDATION

Since cobalamin deficiency and hyperhomocystinemia are prevalent amongst psychiatric patients in our environment, these findings could be used as a basis for the inclusion of prophylactic Vitamin B12 to patients with psychiatric symptoms.

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CHAPTER NINE

LIMITATIONS OF THE STUDY

1 It is essentially a hospital-based study. The results derived after analysis might have been affected by transportation due to the labile nature of cobalamin, homocysteine and folate reactants.

2 The study could have been further enhanced if the following indices were additionally evaluated, but this was limited because of time and finance:

a) Red cell folate assay

b) Serum methylmalonic acid assay

c) 5,10-methylene tetrahydrofolate reductase mutation.

3 Diet is a very relevant and major issue in this study and more especially in psychiatric disorder, because we do know that psychiatric illness can impact negatively on dietary intake. Even at that, given the poor data of the nutritional contents of our main foods will render it challenging to make objective inferences that may be directly related to the biochemical parameters of interest. Since this study did not explore extensively the role of diet and nutrition, future research can explore this challenges.

4 Given the limitation of this study to explore the role of cobalamin, folate, as well as homocysteine levels in the aetiology of psychiatric disorders, further research to establish this gap is indicated. Findings from such research may provide insight into the role of supplementation in the management of psychiatric disorders.

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