Reward Sensitivity

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Reward sensitivity is a biological trait that determines the intensity of our emotional and motivational responses to positive stimuli — such as praise, achievement, or novelty. In the behavioral approach system (BAS), it acts as volume control for how the brain processes potential benefits. In individuals with bipolar disorder, this system is often hypersensitive, meaning the biological circuits governing approach motivation are overly reactive. This sensitivity is considered a stable vulnerability trait or biomarker that remains present even during periods of stable mood (euthymia), rather than just a symptom of an active episode.

• Manic/hypomanic activation: In the reward hypersensitivity model, positive life events (a promotion or new relationship) can cause the reward system to over-activate. This triggers a surge in energy, excessive confidence, and a decreased need for sleep.
• Depressive downregulation: Conversely, this same hypersensitive system can crash or over-deactivate in response to failure, loss, or a lack of reward, leading to the profound motivational deficits and low energy characteristic of bipolar depression.
• Neural basis: This process is linked to the fronto-striatal circuits of the brain — specifically the ventral striatum and orbitofrontal cortex — which are responsible for evaluating reward value and calculating the effort required to obtain it.

Behavioral indicators:

• Confidence surges: Experiencing a disproportionate and prolonged increase in self-worth following minor successes.

• Ambitious goal-striving: Setting exceptionally high or statistically unlikely goals, such as achieving sudden fame or immense wealth.

• Sustained effort: Persisting in a task much longer or harder than average when a reward is possible, even as the difficulty increases.