Understanding the Connections Between Parkinson’s and Depression
The motor symptoms of PD include tremors, stiffness, and slowed movement, but PD can also cause many non-motor symptoms that can profoundly affect quality of life. Depression is one of the most common non-motor symptoms of Parkinson’s disease (PD) and is treatable, yet often overlooked. Sometimes, people with PD can have feelings of sadness and low mood years before motor symptoms even appear.
Symptoms of Depression May Worsen Seasonally
These emotional changes may become worse during certain times of the year, particularly the fall and winter months, when daylight hours shorten, and routines shift. This phenomenon, known as seasonal affective disorder (SAD) or seasonal depression, can add another layer of challenge for people with PD. Understanding how depression (especially seasonal depression) interacts with PD is critical to improving both mental and physical well-being. The good news is that there are things you and your doctor can do to help you feel better, so be sure to address any depression concerns with your health care team.
Signs of Seasonal Depression in People with Parkinson’s
About 50% of people with PD experience some form of depression during their illness. Depression in PD is not simply a reaction to the stress of living with a chronic illness. It is a biological part of the disease itself. PD affects the same brain regions and chemical messengers (dopamine, serotonin, and norepinephrine) that regulate mood and motivation.
Symptoms can range from mild unhappiness to major depressive disorder and may fluctuate over time.
Common signs include:
- Persistent sadness or emptiness
- Loss of interest or pleasure in favorite activities
- Fatigue or loss of energy
- Difficulty concentrating or making decisions
- Feelings of guilt or worthlessness
- Sleep changes (insomnia, excessive sleeping, etc.)
- Appetite or weight changes
- Withdrawal from social contact
Because some of these symptoms overlap with PD itself (like fatigue, slowed movement, or sleep problems), depression is frequently underdiagnosed or mistaken for disease progression. This is why screening for depression should be a routine part of PD care.
Why Depression Happens in PD
It is still not completely clear how depression develops in PD, but there are likely several biological and environmental factors that interact:
- Changes in brain chemistry: PD reduces dopamine and serotonin, two neurotransmitters essential for mood regulation.
- Structural brain changes: Imaging studies show that PD affects areas of the limbic system including the amygdala and prefrontal cortex, which control things like emotion, reward, and motivation.
- Inflammation and stress responses: Chronic inflammation, which has been linked to PD progression, can also alter stress hormones and increase depression risk.
- Psychological and social impact: The daily challenges of PD including loss of independence, changes in work or relationships, and physical limitations, can understandably contribute to emotional distress as well.
All these elements make depression in PD distinct from ordinary sadness. It also means that treatment often requires a multi-faceted approach that addresses both the biological and emotional sides of the disease.
Seasonal Depression
For some people, depression becomes more pronounced at certain times of the year, especially in late fall and winter, when sunlight exposure decreases. This pattern, known as seasonal affective disorder (SAD), is more common in northern latitudes and is thought to result from reduced light exposure affecting internal biological rhythms and serotonin levels.
Symptoms of seasonal depression overlap with typical depression but may include:
- Low energy or increased sleepiness
- Craving carbohydrates or overeating
- Difficulty waking up or maintaining motivation
- Feeling sluggish or detached
- Other symptoms that reliably improve in spring or summer
In PD, this can compound already existing issues. Some people with PD may be particularly sensitive to light changes, possibly because the same dopamine pathways that regulate movement also help regulate circadian rhythm and mood.
The Role of Light, Sleep, and Circadian Rhythms
Light doesn’t just help us see. Light also tells our brain when to release certain hormones and regulate our biological clock. Reduced light exposure in the winter months can disrupt melatonin production and circadian rhythms, leading to sleep problems and lower mood.
In PD, where sleep regulation is already often disrupted, these changes can be even more pronounced. Fragmented sleep and daytime fatigue can further worsen depression, creating a feedback loop that can be hard to break.
Research is ongoing into light therapy, which uses bright, full-spectrum lamps to mimic natural daylight and reset circadian rhythms. For some individuals, especially those with seasonal mood changes, light therapy may offer significant benefit when used consistently under medical guidance.
How Depression Impacts PD Symptoms
Depression can go beyond just mental symptoms and can actually worsen motor and non-motor symptoms of PD as well. Depression in PD can also lead to:
- Poorer motor performance
- Slower walking and reduced balance
- Increased perception of disability
- Lower response to medication and therapy
- Reduced overall quality of life
- More severe fatigue, pain, and cognitive issues.
This interconnection makes treating depression a core part of PD care to treat the whole patient.
Diagnosis and Treatment
The good news is that depression and seasonal depression can be treated in a variety of ways.
Treatment options may include:
Medication:
- Antidepressants such as SSRIs or SNRIs can safely be used in many people with PD.
- Dopamine agonists (used for PD motor symptoms) may also have mild mood-boosting effects.
- Medication plans should always be individualized to avoid unwanted interactions.
Therapy:
- Cognitive Behavioral Therapy (CBT) and other forms of talk therapy can help individuals manage negative thought patterns and regain motivation.
- Support groups (in-person and/or online) can provide social connection and shared understanding (You are not in this alone!).
Lifestyle Changes
- Regular exercise can improve both motor and mood symptoms. (Exercise is critical for people with PD regardless, but the mental and emotional benefits of exercise particularly play a role here.)
- Structured daily routines and outdoor time can help stabilize circadian rhythm.
- Adequate sleep, nutrition, and hydration all play crucial roles in emotional stability.
Light Therapy:
- For those with seasonal depression, light therapy for 20–30 minutes each morning may help restore energy and mood levels.
Always discuss these options with a clinician before implementing them in your treatment plan or care routine.
Ongoing Research and Unanswered Questions
While treatment options exist, researchers are still working to understand why depression occurs in some people with PD and not others. Questions that still remain include:
- How early mood changes might signal future PD development (prodromal depression)
- Whether improving sleep or light exposure can prevent depressive episodes
- How inflammation and gut health may influence brain chemistry and emotional resilience
- What role genetic factors play in vulnerability to seasonal changes
Most importantly, if you notice symptoms of depression, talk with your doctor about them. Depression and seasonal affective disorder are treatable and addressing them can significantly improve daily functioning and quality of life.
Tips & Takeaways
- Depression is a common and treatable symptom of PD affecting approximately 50% of people with the disease.
- Seasonal depression may worsen PD-related mood changes due to light and sleep disruptions.
- Open communication with healthcare providers is essential because treatment is available.
- Depression should be screened for and treated as part of routine PD care.
- Exercise, social connection, and exposure to natural light can meaningfully improve mood.
- Light therapy and antidepressant medication may offer additional relief when used under supervision (always consult a clinician prior to use).
- Ongoing research continues to explore how the brain, environment, and circadian rhythms interact to shape emotional health in PD.
This blog was written by Clark Jones, PhD, and was reviewed, edited, and approved by Dr. Rebecca Gilbert.