Researchers explored how our brain’s reward system connects to depression and other common mental health problems like social anxiety and eating disorders.
They found that a dampened reward response seems to follow, rather than precede, symptoms of depression and other disorders.
This highlights the important role that blunted enjoyment plays in the persistence of mental illness.
Key facts:
- A reduced sensitivity to rewards, known as reward insensitivity, has been linked to depression and other mental health issues. But it’s not clear whether it’s a cause or a consequence of symptoms.
- This study looked at reward sensitivity and symptoms of depression, social anxiety, eating disorders, and alcohol use in over 450 adults over 8 weeks.
- They found that lower reward sensitivity followed increases in depressive symptoms over time, not the other way around.
- Depressive symptoms also explained the link between reward insensitivity and social anxiety and eating disorder symptoms.
- Reward sensitivity was not related to alcohol consumption patterns in this generally healthy sample.
Source: BMC Psychiatry. 2023; 23: 650.
The Brain’s Reward Center
The brain’s reward system motivates us to seek out experiences that feel good, like eating, sex, and socializing.
It uses chemical messengers like dopamine to make us feel pleasure and satisfaction when we engage in these rewarding behaviors.
Over time, this reinforces habits and behaviors that help us survive and pass on our genes.
When working properly, this dopamine-fueled reward system gives zest and meaning to life.
But in some people, it becomes underactive, leading to joyless apathy and lack of motivation.
This “reward deficiency syndrome” has been most studied in the context of depression.
The Blunting Effects of Depression
People with depression often lose interest in normal pleasures, a hallmark symptom called anhedonia.
Research shows they have a dampened response to rewards in the brain’s reward circuitry, especially the ventral striatum and nucleus accumbens regions.
This reward insensitivity may be caused by lower dopamine levels or fewer dopamine receptors.
PET scans show that people with depression have less receptor binding potential for dopamine in the striatum.
Without enough dopamine activation, people miss out on the motivating and uplifting effects of everyday rewards.
This makes depressive symptoms like low energy, sadness, and isolation worse.
Does Blunted Reward Come Before Depression?
Scientists have debated whether reward insensitivity is present before depression arises, making some people vulnerable, or if it develops after depressive symptoms take hold.
This study aimed to clarify the time course of the relationship between reward response and depression severity.
The researchers surveyed over 450 adults online about their mental health symptoms and reward sensitivity at 3 time points spaced 4 weeks apart.
Reward sensitivity was measured with a questionnaire called the Positive Valence System Scale, which asks about enjoyment of things like food, touch, nature, goals, and socializing.
The researchers looked at how well it predicted future depression scores on a standard screening questionnaire called the PHQ-9.
Blunted Reward Follows Depression
They found no evidence that lower reward sensitivity precedes or predicts later depression.
However, higher depression scores did foreshadow decreases in reward sensitivity at the next time point.
This effect grew stronger over time – depression symptoms predicted reward insensitivity more strongly across the full 8 weeks than just in the first 4 weeks.
The same pattern was found for symptoms of social anxiety and eating disorders. But their links to later reward insensitivity were explained by depression severity.
In other words, social anxiety and disordered eating predicted worse depression, which in turn predicted lower reward sensitivity.
Depression acted as a mediator between those disorders and blunted reward response.
No Link Between Reward and Alcohol Use
In contrast to past addiction research, the researchers found no association between reward sensitivity and alcohol consumption patterns in this generally healthy sample.
Drinking habits did not predict future reward sensitivity.
And interestingly, greater reward sensitivity predicted higher drinking over time, opposite of the expected direction.
Limitations and Significance
While this study had a strong longitudinal design, it relied entirely on self-report questionnaires.
It focused on a non-clinical sample who mostly reported mild mental health symptoms.
Replication in clinically diagnosed patients using multi-modal assessments of reward response would provide stronger evidence.
Still, the findings shed light on how blunted enjoyment arises and persists in common mental health disorders.
Rather than a risk factor, reward insensitivity seems to be a consequence of depression that helps maintain it over time.
Targeting this anhedonia in treatment could be key to preventing chronic depression.
A Vicious Cycle That Sustains Depression
These results suggest depression, anxiety, and disordered eating can trigger a vicious cycle:
Symptoms like low mood, isolation, and negative thoughts → reduced enjoyment from everyday activities → worsening symptoms due to lack of reinforcement.
Without feel-good dopamine hits from rewards, people have little respite from their suffering.
This depletion of energy and coping resources makes it harder to heal.
On the other hand, effective treatments may work by restoring reward sensitivity, stimulating dopamine release, and reigniting motivation.
Understanding this self-perpetuating cycle is the first step to breaking it.
Unraveling the Brain’s Reward System
For a complex organ like the brain, no one study tells the whole story.
Let’s break down the key areas and chemicals that regulate motivation and enjoyment.
The Ventral Tegmental Area (VTA)
- This cluster of neurons sits near the base and center of the brain. It’s considered the starting point of the reward pathway.
- The VTA uses dopamine to signal the presence of rewards. Dopamine levels spike when something pleasurable is anticipated or experienced.
The Nucleus Accumbens
- The nucleus accumbens is a hub deep in the forebrain that receives dopamine from the VTA.
- It integrates reward signals and helps determine if something is worth seeking out again to repeat the good feeling.
The Prefrontal Cortex
- This brain region is involved in decision-making, planning, personality, and regulating emotions and impulses.
- It determines the value of expected rewards and sends feedback to the reward system. Decreased signaling may reduce motivation.
Dopamine
- Dopamine is often called the brain’s pleasure and reward chemical. But more accurately, it drives us toward beneficial resources and behaviors needed for survival.
- Besides pleasure, dopamine regulates mood, attention, learning, movement, and more. It takes part in many psychiatric conditions.
- Stress, drug abuse, aging, toxins, and mental illness can all impair healthy dopamine function, lowering motivation and enjoyment of life.
Serotonin, Endorphins, and Oxytocin
- In addition to dopamine, other neurochemicals like serotonin, endorphins, and oxytocin contribute to the overall reward response.
- Low serotonin may play a role in depression and blunted reactiveness to positive experiences.
- Endorphins mask pain and create a sense of euphoria. Oxytocin is involved in social bonding.
Genetics and Environmental Factors
- Research suggests reward sensitivity is partly heritable, but life experiences also shape its development. Childhood adversity and stress can alter the reward pathway early on.
- Genetic variations that reduce dopamine receptors or transporters likely make some people more vulnerable to reward deficits. But social and behavioral factors determine how these genes are expressed.
Restoring Lost Motivation
If impaired reward response keeps mental illness going, what can be done?
Along with therapy and social support, both pharmaceutical and natural remedies hold promise for reawakening pleasure and purpose.
Antidepressants
- Most antidepressants work by increasing serotonin, norepinephrine, and dopamine activity in the brain. This helps normalize reward reactions.
- Wellbutrin, a common antidepressant, blocks dopamine reuptake. This leaves more dopamine in synapses, amplifying signaling.
Brain Stimulation Therapies
- Techniques like repetitive TMS and electroconvulsive therapy may relieve treatment-resistant depression by stimulating reward regions.
- Deep brain stimulation sends electrical impulses to targeted areas. A recent trial found it improved anhedonia, motivation, and mood in depression.
Exercise and Healthy Living
- Aerobic exercise reliably activates feel-good neurochemicals and brain circuits involved in reward, improving pleasure and motivation levels over time.
- Eating a nutritious diet, getting good sleep, avoiding substance abuse, and reducing stress also support natural reward system functioning.
Mindfulness Meditation
- Research indicates mindfulness practices boost dopamine signaling and may reverse depression-associated shrinkage of the nucleus accumbens.
- By training attention on present rewards like breath and sensory input, meditation could counter the negativity bias of depressive rumination.
Rewiring the Habit of Joy
Our brains are always learning – even an “old dog” can pick up new tricks with consistent practice and positive reinforcement.
Just like musicians or athletes, we can train our neural pathways for greater skill, in this case cultivating happiness from within.
While more research is needed, evidence suggests actively re-engaging in pleasurable activities – savoring favorite foods, exploring nature, learning new skills, helping others – can recreate reward response and break the self-perpetuating cycle of anhedonia and depression.
Our brains are shaped by what we do – the habits we build, the thoughts we think, the actions we take.
By rewiring ourselves for regular rewards, we can all tap into the infectious magic of dopamine.
References
- Study: Transdiagnostic considerations of the relationship between reward sensitivity and psychopathological symptoms
- Authors: L. Potsch & W. Rief (2023)
