What is Huntington’s Disease
Huntington’s disease is a rare, genetic neurodegenerative disorder caused by an expansion of a repeating CAG triplet series in the huntingtin gene on chromosome 4. This causes the progressive degeneration of nerve cells in the brain, having a broad impact on the patient’s functional abilities, including motor, cognitive and psychiatric dysfunction.
Huntington’s disease is often called the quintessential family disease as it is inherited in an autosomal dominant fashion, meaning that each child of an affected parent has a 50% chance of inheriting the faulty gene and developing the disease.
As mentioned, Huntington’s disease manifests as a triad of motor, cognitive, and psychiatric symptoms that progresses insidiously over many years. The average length of survival after clinical diagnosis is typically 10 – 20 years. However, some people have lived thirty or forty years with late-stage Huntington’s disease lasting up to a decade or more.
As the disease progresses, a person with Huntington’s disease will eventually require help with all activities of daily living and care, eventually becoming bedridden and unable to speak. Huntington’s disease patients are however able to understand language and have an awareness of family and friends, although some won’t recognize family members.
Death is usually a result of pneumonia or other infections, injuries related to falls, complications related to the inability to swallow and often also suicide.
Symptoms of Huntington’s Disease
Huntington’s disease is often described as having ALS, Parkinson’s and Alzheimer’s simultaneously, with symptoms, usually appearing between the ages of 30 to 50, and worsening over a 10 to 25-year period.
The type of symptoms which appear first as well as symptom severity vary greatly from patient to patient. Some symptoms may also appear more dominant or have a greater effect on functional ability, although this can change during the course of the disease.
- Involuntary jerking or writhing movements (chorea)
- Muscle problems, including rigidity and muscle contracture (dystonia)
- Slow or abnormal eye movements
- Impaired gait, posture and balance
- Issues with speech or speech changes
- Difficulty swallowing
- Ataxia and spasticity
- Muscle weakness, a loss of muscle tissue and weight loss
- Difficulty organizing, prioritizing or focusing on tasks
- Lack of cognitive flexibility or dealing with changes in the environment and/or day-to-day schedule
- The tendency to get stuck on a thought, behaviour or action (perseveration)
- A lack of impulse control resulting in outbursts, acting without thinking and sexual promiscuity
- Lacking awareness of one’s own behaviours and abilities
- Slowness in processing thoughts or ”finding” words
- Difficulty in learning and/or assimilating new information
- Depression occurring due to injury to the brain and subsequent changes in brain function.
- An obsessive-compulsive disorder marked by recurrent, intrusive thoughts and repetitive behaviours
- Mania categorized by an exaggerated elevation in mood, overactivity, impulsive behaviour and inflated self-esteem
- Bipolar disorder with alternating episodes of depression and mania
- Feelings of irritability, sadness or apathy
- Social withdrawal
- Fatigue and loss of energy
- Frequent thoughts of death, dying or suicide
Symptoms of juvenile Huntington’s disease
- Behavioural changes
- Difficulty paying attention
- A rapid, significant drop in overall school performance
- Behavioural problems
- Physical changes
- Contracted and rigid muscles that affect gait (especially in young children)
- Tremors or slight involuntary movements
- Frequent falls or clumsiness
Huntington’s Disease Medications & Treatments
There is no cure for Huntington’s disease and most interventions are aimed at lessening some symptoms of movement and psychiatric disorders. Multiple interventions can help a patient adapt more easily to changes in abilities. However, drugs that treat some symptoms may result in side effects that worsen other symptoms meaning that treatment goals must be regularly reviewed and updated.
Medications for movement disorders
- Tetrabenazine and deutetrabenazine are often prescribed to suppress involuntary jerking and writhing movements (chorea) although they do not have any effect on the progression of the disease. Possible side effects include drowsiness, restlessness, and the risk of worsening or triggering depression or other psychiatric conditions.
- Antipsychotics like haloperidol and fluphenazine can suppress movements that can be beneficial in treating chorea. However, these drugs may worsen involuntary contractions (dystonia), restlessness and drowsiness. Other types of anti-depressant drugs such as risperidone, olanzapine and quetiapine may have fewer side effects but still should be used with caution, as they may also worsen symptoms.
- Other medications that may help suppress chorea include amantadine, levetiracetam and clonazepam although poor side effect profiles limit their use.
Medications for psychiatric disorders
- Antidepressants such drugs as citalopram, escitalopram, fluoxetine and sertraline can help relieve depression but may also have some effect on treating obsessive-compulsive disorder. Side effects may include nausea, diarrhea, drowsiness and low blood pressure.
- Antipsychotic drugs such as quetiapine, risperidone and olanzapine are prescribed to suppress violent outbursts, agitation, and other symptoms of mood disorders or psychosis. However, these drugs may themselves cause a variety of other types of movement disorders.
- Mood-stabilizing drugs and anticonvulsants, such as Divalproex, carbamazepine and lamotrigine can help prevent the highs and lows associated with bipolar disorder.
Additional interventions that can help patients with Huntington’s disease can help them deal with behavioural, cognitive and day-to-day living difficulties. For instance, psychotherapy can help the patient and their families develop coping strategies, manage expectations during the progression of the disease and facilitate effective communication.
Speech can help improve patients’ ability to swallow, eat and speak clearly, or teach them how to use communication devices. Similarly, physical therapy can enhance strength, flexibility, balance and coordination that can help maintain mobility as long as possible and may reduce the risk of injury. In addition, occupational therapy can help with strategies that can assist the patient, family members and caregivers on environmental changes and the use of assistive devices that improve functional abilities, including the installation of handrails at home, assistive devices for activities such as bathing and dressing and eating and drinking utensils adapted for people with limited fine motor skills.
CBD for Huntington’s Disease
Research & Scientific Evidence of using CBD for Huntington’s Disease
Research into the use of cannabidiol (CBD) for Huntington’s disease goes as far back as the 1980s with a few, although sometimes contradicting studies on both animal and human subjects being available. However, most recent studies and clinical trials show that CBD has several properties that can help relieve many symptoms of Huntington’s disease including neurodegeneration, oxidative stress and inflammation as well as motor impairments such as tardive dyskinesia and cognitive decline.
In a 2016 review paper published in Pharmacological Research, the authors evaluated the available evidence showing the CBD’s neuroprotective properties for application in neuropsychiatric disorders. They concluded that CBD has potential therapeutic effects over a broad range of neuropsychiatric disorders including Huntington’s disease.
Although the exact mechanisms are still unclear, from the data available it seems clear that CBD attenuates brain damage associated with neurodegenerative and/or ischemic conditions. This seems to be due to CBD’s ability to affect synaptic plasticity and facilitates neurogenesis through interactions with the endocannabinoid system (ECS), 5HT1A receptors, Oxidative stress and peroxisome proliferator-activated receptors (PPAR), the inhibition of adenosine uptake, immune mediators, brain-derived neurotrophic factor (BDNF), and other related mechanisms.
They also found that CBD also has positive effects on attenuating psychotic-, anxiety- and depressive-like behaviors, which taken together with its neuroprotective and neurogenesis properties, makes CBD a potential therapeutic agent for neuropsychiatric disorders.
In another 2016 study published in Frontiers in Pharmacology, however this time on animals, scientists investigated the efficacy of CBD in preventing motor and cognitive impairments induced in rats.
The induced tardive dyskinesia (motor impairment) is accompanied by cognitive deficits in rats through the repeated administration of reserpine. Male Wistar rats received four injections of CBD (0.5 or 5 mg/kg) or a placebo from day two to five after symptoms onset. On days 3 and 5, the animals also received one injection of 1 mg/kg reserpine or vehicle. Locomotor activity, vacuous chewing movements, and catalepsy were assessed from days one to seven. On days eight and nine, they evaluated animals’ performance on the plus-maze discriminative avoidance task, for learning/memory assessment.
They found that both CBD dosages of 0.5 and 5 mg/kg were able to reduce motor and cognitive impairments that is suggestive of it being an effective and safe pharmacological intervention for reducing tardive dyskinesia and cognitive impairments in neurodegenerative diseases.
In a recent 2018 review paper published in Frontiers in Pharmacology, the authors reviewed clinical and pre-clinical studies and draw attention to the potential of cannabidiol in the prevention and treatment of movement disorders such as Huntingdon’s disease.
From the data, they found that CBD how 51–84% protection against the huntingtin-induced cell death caused by the huntingtin gene that causes Huntington’s disease, possibly by exert a protective effect through antioxidant mechanisms. In addition, they found that CBD reverses or attenuates 3-NP-induced alterations in the mRNA for antioxidant enzymes that reduce striatal (a cluster of neurons in the subcortical basal ganglia of the forebrain) damage and oxidative injury.
They concluded that from the data reviewed CBD plays a protective role in the treatment and/or prevention of some movement disorders and seems to be especially effective in treating both primary and secondary dystonic movements. They do however mention that in the case of Huntington’s disease, combining CBD with Δ9-THC in a 1:1 ratio (as in Sativex) is preferred for optimal benefits.
As with the review study above, most of Huntingdon’s patients that use cannabinoids for symptom relief use medical cannabis or a combination of CBD and THC. However, the internet is full of stories like this one, of people claiming that they have had life-changing improvements in their condition. Nonetheless, for patients that do not have access to medical cannabis, CBD can still be effective for symptom relief at the right dosages.
CBD as a Complementary Treatment in Huntingdon’s disease
In addition, CBD can be helpful as a complementary therapy for patients with Huntington’s disease in other ways. As mentioned, many patients have co-existing conditions like depression, anxiety, and in the case of juvenile Huntington’s, seizures with which CBD can help. CBD’s powerful anticonvulsant properties can help prevent, control and reduce seizures. Similarly, as an anti-depressant, CBD can help alleviate the clinical depression that is commonly experienced with Huntington’s while its anxiolytic properties can help control anxiety and hyperactivity.
To date, research on CBD for Huntington’s disease is still rare, with more focus being on investigating Sativex – a drug with a 1:1 ratio of CBD to THC. However, CBD does have several properties that can directly help manage and reduce many Huntington’s disease symptoms such as oxidative stress, inflammation, tardive dyskinesia, and cognitive decline. For instance, it has repeatedly been shown that CBD has neuroprotective, antispasmodic, anxiolytic, anti-depressant, anti-oxidant, and anti-inflammatory properties. This also makes CBD a powerful ally when used as a complementary therapy for depression and anxiety. If you are considering using CBD for Huntington’s disease, always speak to your treating physician first. CBD is contraindicated with use with certain medications. They can also monitor dosage, symptom severity, and other clinical parameters, to ensure that your CBD treatment is both safe and effective.