Malnourished and psychotic, and found incompetent to stand trial

Mr. N, age 48, has chronic mental illness and has been in and out of psychiatric hospitals for 30 years, with diagnoses of bipolar disorder, not otherwise specified, without psychotic features and schizophrenia. He often is delu­sional and disorganized and does not adhere to treatment. Since age 18, his psychiatric care has been sporadic; during his last admission 3 years ago, he refused treatment and left the hospital against medical advice. Mr. N is homeless and often eats out of a dumpster.

Recently, Mr. N was arrested for cocaine possession, for which he was held in custody. His mental status continued to deteriorate while in jail, where he was evaluated by a forensics examiner.

Mr. N was declared incompetent to stand trial and was transferred to a state psychiatric hospital.

In the hospital, the treatment team finds that Mr. N is disorganized and preoccupied with thoughts of not wanting to “lose control” to the physicians. He shows no evidence of suicidal or homicidal ideation or perceptual disturbance. Mr. N has difficulty grasping con­cepts, making plans, and following through with them. He has poor insight and impulse control and impaired judgment.

Mr. N’s past and present diagnoses include bipolar disorder without psychotic features, schizophrenia, obsessive-compulsive per­sonality disorder, paranoid personality traits, borderline intelligence, cellulitis of both legs, and chronic venous stasis. Although he was arrested for cocaine possession, we are not able to obtain much information about his history of substance abuse because of his poor mental status.

What could be causing Mr. N’s deteriorating mental status?
   a) substance withdrawal
   b) malnutrition
   c) worsening schizophrenia
   d) untreated infection due to cellulitis

HISTORY Sporadic care
Mr. N can provide few details of his early life. He was adopted as a child. He spent time in juvenile detention center. He completed 10th grade but did not graduate from high school. Symptoms of mental illness emerged at age 18. His employment history is consistent with chronic mental illness: His longest job, at a grocery store, lasted only 6 months. He has had multiple admissions to psychiatric hospi­tals. Over the years his treatment has included divalproex sodium, risperidone, paroxetine, chlorpromazine, thioridazine, amitriptyline, methylphenidate, and a multivitamin; how­ever, he often is noncompliant with treatment and was not taking any medications when he arrived at the hospital.

EVALUATION Possible deficiency
The treatment team discusses guardianship, but the public administrator’s office pro­vides little support because of Mr. N’s refusal to stay in one place. He was evicted from his last apartment because of hoarding behav­ior, which created a fire hazard. He has been homeless most of his adult life, which might have significantly restricted his diet.

A routine laboratory workup—complete blood count, basic metabolic panel, liver function test, thyroid-stimulating hormone, and lipids—is ordered, revealing an absolute neutrophil count (ANC) in the low range at 1,200/μL (normal range, 1,500 to 8,000/μL). Mr. N is offered treatment with a long-acting IM injection of risperidone because of his his­tory of noncompliance, but he refuses the medication. Instead, he is started on oral ris­peridone, 2 mg/d.

The cellulitis of both lower limbs and chronic venous stasis are of concern; the med­ical team is consulted. Review of Mr. N’s medi­cal records from an affiliated hospital reveals a history of vitamin B₁₂ deficiency. Further tests show that the vitamin B₁₂ level is low at <50 pg/mL (normal range, 160 to 950 pg/mL). Pernicious anemia had been ruled out after Mr. N tested negative for antibodies to intrin­sic factor (a glycoprotein secreted in the stom­ach that is necessary for absorption of vitamin B₁₂). Suspicion is that vitamin B₁₂ deficiency is caused by Mr. N’s restricted diet in the context of chronic homelessness.

The authors’ observations
A review of the literature on vitamin B₁₂ deficiency describes tingling or numbness, ataxia, and dementia; however, in rare cases, vitamin B₁₂ deficiency presents with psychi­atric symptoms, such as depression, mania, psychosis, dementia, and catatonia.^1-13

We suspected that Mr. N’s vitamin B₁₂ deficiency could have been affecting his mental status; consequently, we ordered routine laboratory work-up that included a complete blood count with differential and peripheral smear, which showed macro­cytic anemia and ovalocytes. We also tested his vitamin B₁₂ level, which was very low at 55 pg/mL. These results, combined with his previously recorded vitamin B₁₂ level (Table 1), suggested deficiency.

TREATMENT Oral medication
Two months after starting risperidone, the medical team recommends IM vitamin B₁₂ as first-line treatment, but Mr. N refuses. We considered guardianship ex parte for invol­untary administration of IM B₁₂ injection to prevent life-threatening consequences of a non-healing ulcer on his leg that was related to his cellulitis. Meanwhile, we reviewed the literature on vitamin B₁₂ therapy, including route, dosage, and outcome.^14-23 Mr. N agrees to oral vitamin B₁₂, 1,000 μg/d,21 and we no longer consider guardianship ex parte. Mr. N’s vitamin B₁₂ level and clinical picture improve 1 month after oral vitamin B₁₂ is added to oral risperidone. His thought process is more orga­nized, he is no longer paranoid, and he shows improved insight and judgement. ANC and neutrophil count improve as well (Table 2). Mr. N’s ulcer begins to heal despite his non­compliance with wound care.

The forensic examiner sees Mr. N after 3 months of continued therapy. His thought pattern is more organized and he is able to comprehend the criminal charges against him and to work with his attorney. He is deter­mined competent by the forensic examiner; in a court hearing, the judge finds Mr. N compe­tent to stand trial.

The authors’ observations
Based on our experience treating Mr. N, we think that it is important to establish an association between vitamin B12 deficiency and psychosis. Vitamin B₁₂ deficiency is uncommon; however, serum levels do not need to be significantly low to pro­duce severe neuropsychiatric morbidity, which has been reported with serum levels ≤457 pg/mL.^2-5,24,25 It is more frequent than the other organic causes of psychosis^5,10,24 and Mr. N’s improvement further strength­ened the correlation.

Parenteral vitamin B₁₂ therapy is the first-line treatment for a deficiency, but oral or sublingual vitamin B₁₂ can be given to patients who are disabled, geriatric, or refuse parenteral administration.²¹ Only approxi­mately 1% of oral vitamin B₁₂ is absorbed in patients who do not have intrinsic factor. The daily requirement of vitamin B₁₂ is 1.0 to 2.5 μg/d; large oral dosages of 1,000 to 5,000 μg/d therefore seem to be effective in correcting deficiency, even in the presence of intrinsic factor deficiency.^15,20,21 Large oral dosages also benefit other hematological abnormalities, such as a low white blood cell count and neutropenia.

How vitamin B12 deficiency affects neuropsychiatric illness
Vitamin B₁₂ is essential for methylation, a process crucial for the formation of neurotransmitters such as serotonin, dopamine, and epinephrine. A low level of vitamin B₁₂ can interrupt methylation and cause accu­mulation of homocysteine and impaired metabolism of serotonin, dopamine, and epinephrine. Hyperhomocysteinemia can contribute to cerebral dysfunction by caus­ing vascular injury.²⁶

Vitamin B₁₂ also is involved in tetrahy­drobiopterin synthesis in the brain, which is pivotal for synthesis of monoamine neu­rotransmitters. Vitamin B₁₂ deficiency can lead to accumulation of methyltetrahydro­folate, an excitatory neurotoxin. All of these can contribute to development of psychosis. Therefore, a defect in the methylation process could be responsible for the neuropsychiat­ric manifestations of vitamin B₁₂ deficiency.

What did we learn from Mr. N?
In most people, vitamin B₁₂ levels are normal, however, we recommend that clinicians con­sider vitamin B₁₂ deficiency when a patient has new-onset or unresponsive psychosis,²⁷ particularly in a homeless person or one who has a restricted diet.²⁸ It is important to rule out vitamin B₁₂ deficiency in a patient with a low serum folate level because folic acid therapy could exacerbate neurologic manifestations of underlying vitamin B₁₂ deficiency and increase the risk of perma­nent nerve damage and cognitive decline.

We were intrigued to see improvement in Mr. N after we added vitamin B₁₂ to his ongoing treatment with an antipsychotic. We did not believe that vitamin B₁₂ supple­mentation was the sole reason his mental status improved enough to be found com­petent to stand trial, although we believe that initiating oral vitamin B₁₂ was benefi­cial for Mr. N.

Last, this case supports the need for research to further explore the role of vita­min B₁₂ in refractory psychosis, depression, and mania.

Bottom Line
Vitamin B₁₂ deficiency can contribute to psychosis and other psychiatric disorders, especially in patients with a restricted diet, such as those who are homeless. Parenteral vitamin B₁₂ therapy is the first-line treatment, but oral supplementation can be used if the patient refuses therapy. Large oral dosages of 1,000 to 5,000 μg/d seem to be effective in correcting vitamin B₁₂ deficiency.

Related Resources
• Ramsey D, Muskin PR. Vitamin deficiencies and mental health: How are they linked? Current Psychiatry. 2013;12(1):37-43.
• Lindenbaum J, Healton EB, Savage DG, et al. Neuropsychiatric disorders caused by cobalamin deficiency in the absence of anemia or macrocytosis. N Engl J Med. 1988;318(26):1720-1728.

Drug Brand Names
Amitriptyline • Elavil                                      
Chlorpromazine • Thorazine                             
Divalproex sodium • Depakote
Methylphenidate • Ritalin
Paroxetine • Paxil                      
Risperidone • Risperdal
Thioridazine • Mellaril

Acknowledgements
The authors thank Jan Jill-Jordan, PhD, for her help preparing the manuscript of this article.

Disclosures
The authors report no financial relationships with any company whose products are mentioned in this article or with manufacturers of competing products.

Mr. N, age 48, has chronic mental illness and has been in and out of psychiatric hospitals for 30 years, with diagnoses of bipolar disorder, not otherwise specified, without psychotic features and schizophrenia. He often is delu­sional and disorganized and does not adhere to treatment. Since age 18, his psychiatric care has been sporadic; during his last admission 3 years ago, he refused treatment and left the hospital against medical advice. Mr. N is homeless and often eats out of a dumpster.

Recently, Mr. N was arrested for cocaine possession, for which he was held in custody. His mental status continued to deteriorate while in jail, where he was evaluated by a forensics examiner.

Mr. N was declared incompetent to stand trial and was transferred to a state psychiatric hospital.

In the hospital, the treatment team finds that Mr. N is disorganized and preoccupied with thoughts of not wanting to “lose control” to the physicians. He shows no evidence of suicidal or homicidal ideation or perceptual disturbance. Mr. N has difficulty grasping con­cepts, making plans, and following through with them. He has poor insight and impulse control and impaired judgment.

Mr. N’s past and present diagnoses include bipolar disorder without psychotic features, schizophrenia, obsessive-compulsive per­sonality disorder, paranoid personality traits, borderline intelligence, cellulitis of both legs, and chronic venous stasis. Although he was arrested for cocaine possession, we are not able to obtain much information about his history of substance abuse because of his poor mental status.

What could be causing Mr. N’s deteriorating mental status?
   a) substance withdrawal
   b) malnutrition
   c) worsening schizophrenia
   d) untreated infection due to cellulitis

HISTORY Sporadic care
Mr. N can provide few details of his early life. He was adopted as a child. He spent time in juvenile detention center. He completed 10th grade but did not graduate from high school. Symptoms of mental illness emerged at age 18. His employment history is consistent with chronic mental illness: His longest job, at a grocery store, lasted only 6 months. He has had multiple admissions to psychiatric hospi­tals. Over the years his treatment has included divalproex sodium, risperidone, paroxetine, chlorpromazine, thioridazine, amitriptyline, methylphenidate, and a multivitamin; how­ever, he often is noncompliant with treatment and was not taking any medications when he arrived at the hospital.

EVALUATION Possible deficiency
The treatment team discusses guardianship, but the public administrator’s office pro­vides little support because of Mr. N’s refusal to stay in one place. He was evicted from his last apartment because of hoarding behav­ior, which created a fire hazard. He has been homeless most of his adult life, which might have significantly restricted his diet.

A routine laboratory workup—complete blood count, basic metabolic panel, liver function test, thyroid-stimulating hormone, and lipids—is ordered, revealing an absolute neutrophil count (ANC) in the low range at 1,200/μL (normal range, 1,500 to 8,000/μL). Mr. N is offered treatment with a long-acting IM injection of risperidone because of his his­tory of noncompliance, but he refuses the medication. Instead, he is started on oral ris­peridone, 2 mg/d.

The cellulitis of both lower limbs and chronic venous stasis are of concern; the med­ical team is consulted. Review of Mr. N’s medi­cal records from an affiliated hospital reveals a history of vitamin B₁₂ deficiency. Further tests show that the vitamin B₁₂ level is low at <50 pg/mL (normal range, 160 to 950 pg/mL). Pernicious anemia had been ruled out after Mr. N tested negative for antibodies to intrin­sic factor (a glycoprotein secreted in the stom­ach that is necessary for absorption of vitamin B₁₂). Suspicion is that vitamin B₁₂ deficiency is caused by Mr. N’s restricted diet in the context of chronic homelessness.

The authors’ observations
A review of the literature on vitamin B₁₂ deficiency describes tingling or numbness, ataxia, and dementia; however, in rare cases, vitamin B₁₂ deficiency presents with psychi­atric symptoms, such as depression, mania, psychosis, dementia, and catatonia.^1-13

We suspected that Mr. N’s vitamin B₁₂ deficiency could have been affecting his mental status; consequently, we ordered routine laboratory work-up that included a complete blood count with differential and peripheral smear, which showed macro­cytic anemia and ovalocytes. We also tested his vitamin B₁₂ level, which was very low at 55 pg/mL. These results, combined with his previously recorded vitamin B₁₂ level (Table 1), suggested deficiency.

TREATMENT Oral medication
Two months after starting risperidone, the medical team recommends IM vitamin B₁₂ as first-line treatment, but Mr. N refuses. We considered guardianship ex parte for invol­untary administration of IM B₁₂ injection to prevent life-threatening consequences of a non-healing ulcer on his leg that was related to his cellulitis. Meanwhile, we reviewed the literature on vitamin B₁₂ therapy, including route, dosage, and outcome.^14-23 Mr. N agrees to oral vitamin B₁₂, 1,000 μg/d,21 and we no longer consider guardianship ex parte. Mr. N’s vitamin B₁₂ level and clinical picture improve 1 month after oral vitamin B₁₂ is added to oral risperidone. His thought process is more orga­nized, he is no longer paranoid, and he shows improved insight and judgement. ANC and neutrophil count improve as well (Table 2). Mr. N’s ulcer begins to heal despite his non­compliance with wound care.

The forensic examiner sees Mr. N after 3 months of continued therapy. His thought pattern is more organized and he is able to comprehend the criminal charges against him and to work with his attorney. He is deter­mined competent by the forensic examiner; in a court hearing, the judge finds Mr. N compe­tent to stand trial.

The authors’ observations
Based on our experience treating Mr. N, we think that it is important to establish an association between vitamin B12 deficiency and psychosis. Vitamin B₁₂ deficiency is uncommon; however, serum levels do not need to be significantly low to pro­duce severe neuropsychiatric morbidity, which has been reported with serum levels ≤457 pg/mL.^2-5,24,25 It is more frequent than the other organic causes of psychosis^5,10,24 and Mr. N’s improvement further strength­ened the correlation.

Parenteral vitamin B₁₂ therapy is the first-line treatment for a deficiency, but oral or sublingual vitamin B₁₂ can be given to patients who are disabled, geriatric, or refuse parenteral administration.²¹ Only approxi­mately 1% of oral vitamin B₁₂ is absorbed in patients who do not have intrinsic factor. The daily requirement of vitamin B₁₂ is 1.0 to 2.5 μg/d; large oral dosages of 1,000 to 5,000 μg/d therefore seem to be effective in correcting deficiency, even in the presence of intrinsic factor deficiency.^15,20,21 Large oral dosages also benefit other hematological abnormalities, such as a low white blood cell count and neutropenia.

How vitamin B12 deficiency affects neuropsychiatric illness
Vitamin B₁₂ is essential for methylation, a process crucial for the formation of neurotransmitters such as serotonin, dopamine, and epinephrine. A low level of vitamin B₁₂ can interrupt methylation and cause accu­mulation of homocysteine and impaired metabolism of serotonin, dopamine, and epinephrine. Hyperhomocysteinemia can contribute to cerebral dysfunction by caus­ing vascular injury.²⁶

Vitamin B₁₂ also is involved in tetrahy­drobiopterin synthesis in the brain, which is pivotal for synthesis of monoamine neu­rotransmitters. Vitamin B₁₂ deficiency can lead to accumulation of methyltetrahydro­folate, an excitatory neurotoxin. All of these can contribute to development of psychosis. Therefore, a defect in the methylation process could be responsible for the neuropsychiat­ric manifestations of vitamin B₁₂ deficiency.

What did we learn from Mr. N?
In most people, vitamin B₁₂ levels are normal, however, we recommend that clinicians con­sider vitamin B₁₂ deficiency when a patient has new-onset or unresponsive psychosis,²⁷ particularly in a homeless person or one who has a restricted diet.²⁸ It is important to rule out vitamin B₁₂ deficiency in a patient with a low serum folate level because folic acid therapy could exacerbate neurologic manifestations of underlying vitamin B₁₂ deficiency and increase the risk of perma­nent nerve damage and cognitive decline.

We were intrigued to see improvement in Mr. N after we added vitamin B₁₂ to his ongoing treatment with an antipsychotic. We did not believe that vitamin B₁₂ supple­mentation was the sole reason his mental status improved enough to be found com­petent to stand trial, although we believe that initiating oral vitamin B₁₂ was benefi­cial for Mr. N.

Last, this case supports the need for research to further explore the role of vita­min B₁₂ in refractory psychosis, depression, and mania.

Bottom Line
Vitamin B₁₂ deficiency can contribute to psychosis and other psychiatric disorders, especially in patients with a restricted diet, such as those who are homeless. Parenteral vitamin B₁₂ therapy is the first-line treatment, but oral supplementation can be used if the patient refuses therapy. Large oral dosages of 1,000 to 5,000 μg/d seem to be effective in correcting vitamin B₁₂ deficiency.

Related Resources
• Ramsey D, Muskin PR. Vitamin deficiencies and mental health: How are they linked? Current Psychiatry. 2013;12(1):37-43.
• Lindenbaum J, Healton EB, Savage DG, et al. Neuropsychiatric disorders caused by cobalamin deficiency in the absence of anemia or macrocytosis. N Engl J Med. 1988;318(26):1720-1728.

Drug Brand Names
Amitriptyline • Elavil                                      
Chlorpromazine • Thorazine                             
Divalproex sodium • Depakote
Methylphenidate • Ritalin
Paroxetine • Paxil                      
Risperidone • Risperdal
Thioridazine • Mellaril

Acknowledgements
The authors thank Jan Jill-Jordan, PhD, for her help preparing the manuscript of this article.

Disclosures
The authors report no financial relationships with any company whose products are mentioned in this article or with manufacturers of competing products.

Mr. N, age 48, has chronic mental illness and has been in and out of psychiatric hospitals for 30 years, with diagnoses of bipolar disorder, not otherwise specified, without psychotic features and schizophrenia. He often is delu­sional and disorganized and does not adhere to treatment. Since age 18, his psychiatric care has been sporadic; during his last admission 3 years ago, he refused treatment and left the hospital against medical advice. Mr. N is homeless and often eats out of a dumpster.

Recently, Mr. N was arrested for cocaine possession, for which he was held in custody. His mental status continued to deteriorate while in jail, where he was evaluated by a forensics examiner.

Mr. N was declared incompetent to stand trial and was transferred to a state psychiatric hospital.

In the hospital, the treatment team finds that Mr. N is disorganized and preoccupied with thoughts of not wanting to “lose control” to the physicians. He shows no evidence of suicidal or homicidal ideation or perceptual disturbance. Mr. N has difficulty grasping con­cepts, making plans, and following through with them. He has poor insight and impulse control and impaired judgment.

Mr. N’s past and present diagnoses include bipolar disorder without psychotic features, schizophrenia, obsessive-compulsive per­sonality disorder, paranoid personality traits, borderline intelligence, cellulitis of both legs, and chronic venous stasis. Although he was arrested for cocaine possession, we are not able to obtain much information about his history of substance abuse because of his poor mental status.

What could be causing Mr. N’s deteriorating mental status?
   a) substance withdrawal
   b) malnutrition
   c) worsening schizophrenia
   d) untreated infection due to cellulitis

HISTORY Sporadic care
Mr. N can provide few details of his early life. He was adopted as a child. He spent time in juvenile detention center. He completed 10th grade but did not graduate from high school. Symptoms of mental illness emerged at age 18. His employment history is consistent with chronic mental illness: His longest job, at a grocery store, lasted only 6 months. He has had multiple admissions to psychiatric hospi­tals. Over the years his treatment has included divalproex sodium, risperidone, paroxetine, chlorpromazine, thioridazine, amitriptyline, methylphenidate, and a multivitamin; how­ever, he often is noncompliant with treatment and was not taking any medications when he arrived at the hospital.

EVALUATION Possible deficiency
The treatment team discusses guardianship, but the public administrator’s office pro­vides little support because of Mr. N’s refusal to stay in one place. He was evicted from his last apartment because of hoarding behav­ior, which created a fire hazard. He has been homeless most of his adult life, which might have significantly restricted his diet.

A routine laboratory workup—complete blood count, basic metabolic panel, liver function test, thyroid-stimulating hormone, and lipids—is ordered, revealing an absolute neutrophil count (ANC) in the low range at 1,200/μL (normal range, 1,500 to 8,000/μL). Mr. N is offered treatment with a long-acting IM injection of risperidone because of his his­tory of noncompliance, but he refuses the medication. Instead, he is started on oral ris­peridone, 2 mg/d.

The cellulitis of both lower limbs and chronic venous stasis are of concern; the med­ical team is consulted. Review of Mr. N’s medi­cal records from an affiliated hospital reveals a history of vitamin B₁₂ deficiency. Further tests show that the vitamin B₁₂ level is low at <50 pg/mL (normal range, 160 to 950 pg/mL). Pernicious anemia had been ruled out after Mr. N tested negative for antibodies to intrin­sic factor (a glycoprotein secreted in the stom­ach that is necessary for absorption of vitamin B₁₂). Suspicion is that vitamin B₁₂ deficiency is caused by Mr. N’s restricted diet in the context of chronic homelessness.

The authors’ observations
A review of the literature on vitamin B₁₂ deficiency describes tingling or numbness, ataxia, and dementia; however, in rare cases, vitamin B₁₂ deficiency presents with psychi­atric symptoms, such as depression, mania, psychosis, dementia, and catatonia.^1-13

We suspected that Mr. N’s vitamin B₁₂ deficiency could have been affecting his mental status; consequently, we ordered routine laboratory work-up that included a complete blood count with differential and peripheral smear, which showed macro­cytic anemia and ovalocytes. We also tested his vitamin B₁₂ level, which was very low at 55 pg/mL. These results, combined with his previously recorded vitamin B₁₂ level (Table 1), suggested deficiency.

TREATMENT Oral medication
Two months after starting risperidone, the medical team recommends IM vitamin B₁₂ as first-line treatment, but Mr. N refuses. We considered guardianship ex parte for invol­untary administration of IM B₁₂ injection to prevent life-threatening consequences of a non-healing ulcer on his leg that was related to his cellulitis. Meanwhile, we reviewed the literature on vitamin B₁₂ therapy, including route, dosage, and outcome.^14-23 Mr. N agrees to oral vitamin B₁₂, 1,000 μg/d,21 and we no longer consider guardianship ex parte. Mr. N’s vitamin B₁₂ level and clinical picture improve 1 month after oral vitamin B₁₂ is added to oral risperidone. His thought process is more orga­nized, he is no longer paranoid, and he shows improved insight and judgement. ANC and neutrophil count improve as well (Table 2). Mr. N’s ulcer begins to heal despite his non­compliance with wound care.

The forensic examiner sees Mr. N after 3 months of continued therapy. His thought pattern is more organized and he is able to comprehend the criminal charges against him and to work with his attorney. He is deter­mined competent by the forensic examiner; in a court hearing, the judge finds Mr. N compe­tent to stand trial.

The authors’ observations
Based on our experience treating Mr. N, we think that it is important to establish an association between vitamin B12 deficiency and psychosis. Vitamin B₁₂ deficiency is uncommon; however, serum levels do not need to be significantly low to pro­duce severe neuropsychiatric morbidity, which has been reported with serum levels ≤457 pg/mL.^2-5,24,25 It is more frequent than the other organic causes of psychosis^5,10,24 and Mr. N’s improvement further strength­ened the correlation.

Parenteral vitamin B₁₂ therapy is the first-line treatment for a deficiency, but oral or sublingual vitamin B₁₂ can be given to patients who are disabled, geriatric, or refuse parenteral administration.²¹ Only approxi­mately 1% of oral vitamin B₁₂ is absorbed in patients who do not have intrinsic factor. The daily requirement of vitamin B₁₂ is 1.0 to 2.5 μg/d; large oral dosages of 1,000 to 5,000 μg/d therefore seem to be effective in correcting deficiency, even in the presence of intrinsic factor deficiency.^15,20,21 Large oral dosages also benefit other hematological abnormalities, such as a low white blood cell count and neutropenia.

How vitamin B12 deficiency affects neuropsychiatric illness
Vitamin B₁₂ is essential for methylation, a process crucial for the formation of neurotransmitters such as serotonin, dopamine, and epinephrine. A low level of vitamin B₁₂ can interrupt methylation and cause accu­mulation of homocysteine and impaired metabolism of serotonin, dopamine, and epinephrine. Hyperhomocysteinemia can contribute to cerebral dysfunction by caus­ing vascular injury.²⁶

Vitamin B₁₂ also is involved in tetrahy­drobiopterin synthesis in the brain, which is pivotal for synthesis of monoamine neu­rotransmitters. Vitamin B₁₂ deficiency can lead to accumulation of methyltetrahydro­folate, an excitatory neurotoxin. All of these can contribute to development of psychosis. Therefore, a defect in the methylation process could be responsible for the neuropsychiat­ric manifestations of vitamin B₁₂ deficiency.

What did we learn from Mr. N?
In most people, vitamin B₁₂ levels are normal, however, we recommend that clinicians con­sider vitamin B₁₂ deficiency when a patient has new-onset or unresponsive psychosis,²⁷ particularly in a homeless person or one who has a restricted diet.²⁸ It is important to rule out vitamin B₁₂ deficiency in a patient with a low serum folate level because folic acid therapy could exacerbate neurologic manifestations of underlying vitamin B₁₂ deficiency and increase the risk of perma­nent nerve damage and cognitive decline.

We were intrigued to see improvement in Mr. N after we added vitamin B₁₂ to his ongoing treatment with an antipsychotic. We did not believe that vitamin B₁₂ supple­mentation was the sole reason his mental status improved enough to be found com­petent to stand trial, although we believe that initiating oral vitamin B₁₂ was benefi­cial for Mr. N.

Last, this case supports the need for research to further explore the role of vita­min B₁₂ in refractory psychosis, depression, and mania.

Bottom Line
Vitamin B₁₂ deficiency can contribute to psychosis and other psychiatric disorders, especially in patients with a restricted diet, such as those who are homeless. Parenteral vitamin B₁₂ therapy is the first-line treatment, but oral supplementation can be used if the patient refuses therapy. Large oral dosages of 1,000 to 5,000 μg/d seem to be effective in correcting vitamin B₁₂ deficiency.

Related Resources
• Ramsey D, Muskin PR. Vitamin deficiencies and mental health: How are they linked? Current Psychiatry. 2013;12(1):37-43.
• Lindenbaum J, Healton EB, Savage DG, et al. Neuropsychiatric disorders caused by cobalamin deficiency in the absence of anemia or macrocytosis. N Engl J Med. 1988;318(26):1720-1728.

Drug Brand Names
Amitriptyline • Elavil                                      
Chlorpromazine • Thorazine                             
Divalproex sodium • Depakote
Methylphenidate • Ritalin
Paroxetine • Paxil                      
Risperidone • Risperdal
Thioridazine • Mellaril

Acknowledgements
The authors thank Jan Jill-Jordan, PhD, for her help preparing the manuscript of this article.

Disclosures
The authors report no financial relationships with any company whose products are mentioned in this article or with manufacturers of competing products.