Many rare diseases are in dire need of need of viable treatments. To fix this problem, researchers have began creating and indicating existing treatments for rare diseases. An example would be utilizing an anti-depressant as a treatment for Rett syndrome. According to an article in Rett Syndrome News, researchers have done just that and indicated mirtazapine, an anti-depressant, as a therapy for Rett syndrome.

About Rett Syndrome

Rett syndrome is a severe, rare neurological disorder that primarily affects females. It was once thought to be a form of autism, but has since been distinguished as its own disorder. It is a genetic disorder, with a mutation occurring on the X chromosome. The exact location of this mutation and its effects are unknown, but researchers do know that it is typically a sporadic mutation. Symptoms of this condition usually appear between the first 12-18 months of life. Effects include slowed brain growth, a small head, issues with muscle coordination, social anxiety, lack of language skills, seizures, uncoordinated breathing, and a tense or irritable disposition.

After these symptoms are noticed, doctors will conduct a clinical examination and rule out other conditions, such as autism. Genetic testing will be used to confirm, and it can also show the severity of a specific case. There is no cure for Rett syndrome, and treatment consists of symptom management. Doctors will suggest physical, speech, and occupational therapy. They may also prescribe anti-seizure medications.

Anti-Depressants for Rett Syndrome

Researchers found that mirtazapine was able to preserve respiratory and motor function and social behavior in both mice and females with Rett syndrome. The full study was published in the Journal of Neurodevelopmental Disorders.

Previous research has proven that levels of certain neurotransmitters that play a role in mood are lower in human and mouse models of Rett syndrome. In order to investigate this, researchers treated mouse models with desipramine (an anti-depressant) and saw positive results. Unfortunately, these results did not translate to their Phase 2 trial, and the serious adverse effects forced the trial to end.

Italian researchers saw that effort, and decided to try a different anti-depressant: mirtazapine. They evaluated its effect on female mouse models by assessing the mice’s motor coordination both before and after the study. There were two ways to test this: the horizontal bar and the dowel test.

They were assessed using a delta score, meaning that a negative score represents a decrease in ability, a zero means no change, and a positive score means an increase in ability. Both tests showed that mice with Rett syndrome that were left untreated had a negative score, control mice had optimal performances each time, and mice with Rett syndrome who did receive treatment either achieved a zero or a positive score.

Further tests were conducted after the study concluded: the open field test, rod walk test, and nest-building test. Results include:

• Mice with Rett syndrome performed worse than the control mice in the open field test, meaning they have more anxiety and less desire to explore.
• No difference in performance between the two groups in the nest-building test.
• Mice with Rett syndrome performed worse than the control mice in the rod walk test, meaning they have less motor coordination.
• Mirtazapine had no impact on any of the tests

Testing Mirtazapine in Females with Rett Syndrome

After seeing the results from trials with mouse models, researchers looked towards how mirtazapine affects females with Rett syndrome. 80 Rett syndrome patients were included in the study, half of which already took the anti-depressant for either poor sleep, anxiety, or mood disorders. Researchers used the motor behavioral assessment scale (MBAS) and Rett clinical severity scale (RCSS) to assess patients.

The half of patients who were taking the medication took an average of 11.72 mg per day and had been taking it for a mean of 1.6 years. 36 of them remained in the study for its entirety, while four dropped out due to anxiety. Results found that:

• Patients not being treated with mirtazapine performed worse on the RCSS and MBAS.
• Patients on the anti-depressant performed better on the two scales regardless of dosage and duration of treatment
• Mirtazapine decreased sleep and mood disturbances

Overall, researchers came to the conclusion that this treatment is not only treating issues that it was prescribed for, but it may also treat the behavioral abnormalities that affect Rett syndrome patients. Hopefully there are future studies to fully investigate anti-depressants as treatments for this condition.