Winding path symbolizing neurological challenges leading to mental well-being.

Beyond the Physical: Understanding Depression in SMON Patients

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Samir D’Costa in Health & Wellness June 2025 • 4 min read.

"Decades after clioquinol intoxication, Japanese SMON patients face unique mental health challenges linked to physical disabilities."


Subacute myelo-optico-neuropathy (SMON), a disease resulting from clioquinol intoxication, primarily affected individuals in Japan from the 1950s to the 1970s. SMON is characterized by sensory and motor disturbances, visual impairment, and abdominal symptoms.

Following the ban on clioquinol-containing drugs in 1970, the incidence of new SMON cases sharply declined. However, the sequelae of this condition continue to impact the lives of thousands of Japanese patients, with the mean age of affected individuals exceeding 80 years in 2016.

These patients often grapple with a multitude of mental and physical complications, including a significantly higher prevalence of major depressive disorder compared to their non-SMON counterparts. Understanding the interplay between physical disabilities and mental health in this population is crucial for providing comprehensive care and improving their quality of life.

The Link Between Physical Disabilities and Depression

Winding path symbolizing neurological challenges leading to mental well-being.

A recent study published in Internal Medicine (2018) sheds light on the intricate relationship between physical disabilities and depressive mental states in Japanese patients with SMON. The study, led by Tetsuro Konishi, aimed to clarify the clinical conditions associated with depression in these patients, who experienced clioquinol intoxication over 40 years ago. The researchers hypothesized that the severity of physical limitations directly impacts the mental well-being of individuals with SMON.

To investigate this connection, the researchers followed 25 Japanese SMON patients with a mean age of 77.2 years. The study utilized the Japanese version of the Zung Self-rating Depression Scale (J-SDS) questionnaires, combined with supportive interviews conducted by a clinical psychotherapist and reviews of medical checkup records. These assessments were repeated multiple times over a period of 2 to 11 years.

  • J-SDS Questionnaires: Patients completed the J-SDS, a tool designed to measure the severity of depressive symptoms.
  • Supportive Interviews: A clinical psychotherapist conducted supportive interviews, providing a safe space for patients to discuss their problems and concerns.
  • Medical Checkup Records: Researchers reviewed medical records to assess the physical condition of the patients, including the severity of SMON symptoms and any gait disturbances.
  • Comparison Group: To provide context, the J-SDS questionnaires were also administered to a control group of 25 age-matched non-SMON elderly individuals.
The study revealed several key findings. While the total J-SDS scores of most SMON patients tended to decrease with age, indicating an improvement in their depressive mental state, their scores remained significantly higher than those of the age-matched healthy elderly people. More importantly, the study found a significant correlation between the total J-SDS scores and the degree of physical disability. Patients with more severe physical limitations, as indicated by lower Barthel index scores, greater SMON severity, and gait disturbances, exhibited higher J-SDS scores, reflecting a greater degree of depression.

Implications for Care and Support

The findings of this study underscore the importance of addressing the mental health needs of SMON patients, particularly in light of their physical limitations. Regular mental health assessments, supportive interviews, and medical examinations are essential for identifying and managing depression in this population. Healthcare providers should consider the impact of physical disabilities on mental well-being and tailor treatment plans accordingly. Strategies for improving physical function, such as physical therapy and assistive devices, may also indirectly improve mental health by reducing limitations and enhancing independence. Furthermore, social support and engagement in meaningful activities can help to combat feelings of isolation and hopelessness.

About this Article -

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Everything You Need To Know

1

What is Subacute myelo-optico-neuropathy (SMON), and what caused it?

Subacute myelo-optico-neuropathy (SMON) is a disease that primarily affected individuals in Japan from the 1950s to the 1970s. It is characterized by sensory and motor disturbances, visual impairment, and abdominal symptoms. The cause of SMON was clioquinol intoxication, a medication that was later banned.

2

How does SMON impact the mental health of those affected, and what does the study by Tetsuro Konishi reveal?

SMON patients often experience a higher prevalence of major depressive disorder. The study led by Tetsuro Konishi investigated the relationship between physical disabilities and depressive mental states in these patients. The research found a significant correlation between the severity of physical limitations and higher J-SDS scores, indicating a greater degree of depression. Patients with more severe physical limitations showed higher levels of depression.

3

What methods were used in the study to assess the mental and physical conditions of SMON patients?

The study used several methods to assess the condition of SMON patients. Patients completed the Japanese version of the Zung Self-rating Depression Scale (J-SDS) questionnaires to measure depressive symptoms. Supportive interviews were conducted by a clinical psychotherapist. Medical checkup records were also reviewed to assess the physical condition, including the severity of SMON symptoms and gait disturbances. The study also included a comparison group of age-matched non-SMON elderly individuals.

4

What specific physical disabilities were linked to higher levels of depression in SMON patients?

The study found that several physical limitations correlated with increased depression. These included lower Barthel index scores, indicating greater physical disability, greater SMON severity, and the presence of gait disturbances. These findings highlight the significant impact of physical limitations on the mental well-being of those suffering from SMON.

5

What are the implications for care and support of SMON patients based on the study's findings?

The study underscores the importance of addressing the mental health needs of SMON patients, particularly in light of their physical limitations. Regular mental health assessments, supportive interviews, and medical examinations are essential for identifying and managing depression. Healthcare providers should consider the impact of physical disabilities on mental well-being and tailor treatment plans accordingly. Strategies for improving physical function, such as physical therapy and assistive devices, may indirectly improve mental health. Social support and engagement in meaningful activities can also combat feelings of isolation and hopelessness.

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