August 30, 2021 • 1hr 28min

Dr. Robert Sapolsky: Science of Stress, Testosterone & Free Will

Huberman Lab

In this episode, Dr. Andrew Huberman interviews Dr. Robert Sapolsky, professor of biology and neurosurgery at Stanford University. Dr. Sapolsky is a renowned expert on stress, hormones, and primate behavior. The wide-ranging conversation covers topics including the biology of stress, the effects of testosterone and estrogen, stress mitigation techniques, and the concept of free will. Dr. Sapolsky shares insights from his decades of research on both humans and baboons to illuminate how our biology and environment shape our behavior.

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Key Takeaways

Stress has both short-term benefits and long-term drawbacks. Short-term stress can enhance mental acuity and focus, while chronic long-term stress is detrimental to health.
Testosterone does not directly cause aggression, but rather amplifies pre-existing aggressive tendencies and lowers the threshold for aggressive responses.
Estrogen has numerous beneficial effects on brain and body health, including enhancing cognition, stimulating neurogenesis, and protecting against cardiovascular disease. However, timing is critical for estrogen replacement therapy.
Stress mitigation techniques are highly individual. What works for one person may not work for another. The key is finding techniques you enjoy and can practice consistently.
Our perception and interpretation of events significantly impacts our physiological stress response. Having a sense of control and predictability can reduce the negative effects of stressors.
Dr. Sapolsky argues we do not have free will in the traditional sense, as our behaviors and choices are the result of complex biological and environmental factors outside our control. However, understanding this can still lead to positive change.
Knowledge itself can be a powerful tool for changing our brains and behaviors. Simply learning about neuroplasticity and the potential for change can make us more open to positive influences.

Introduction

In this episode, Dr. Andrew Huberman interviews Dr. Robert Sapolsky, professor of biology and neurosurgery at Stanford University. Dr. Sapolsky is a renowned expert on stress, hormones, and primate behavior. The wide-ranging conversation covers topics including the biology of stress, the effects of testosterone and estrogen, stress mitigation techniques, and the concept of free will. Dr. Sapolsky shares insights from his decades of research on both humans and baboons to illuminate how our biology and environment shape our behavior.

Topics Discussed

Short-Term vs. Long-Term Stress (7:03)

Dr. Sapolsky explains the difference between short-term and long-term stress:

Short-term stress has beneficial effects like enhanced focus and mental acuity
Long-term chronic stress is detrimental to health
The transition point from short to long-term stress is somewhat arbitrary
Most chronic stressors people deal with are clearly in the long-term range (e.g. daily traffic, abusive boss)

He notes that some stress can be positive, what we call "stimulation." There's an optimal level of stimulation, with too little leading to boredom and too much leading to stress.

The Biology of Valence (9:31)

Dr. Huberman asks about the biological basis for why we perceive some stressful events as positive and others as negative. Dr. Sapolsky explains:

The physiological response looks very similar for both positive and negative stressful events
The key difference appears to be in amygdala activation
"If the amygdala is part of the activation, this is something that's going to be counting as adverse"
The amygdala acts as a "checkpoint" in determining if we interpret something as excitement or terror

Testosterone and Aggression (11:23)

Dr. Sapolsky challenges common misconceptions about testosterone and aggression:

Testosterone does not directly cause aggression
Rather, it lowers the threshold for aggressive responses
It amplifies pre-existing patterns of aggression
In the amygdala, testosterone increases the firing rate of neurons that are already activated
"It's not creating aggression, it's just upping the volume of whatever aggression is already there."

Testosterone and Social Behavior (16:00)

Dr. Sapolsky discusses how testosterone relates to social status and behavior:

Relative testosterone levels between individuals correlate somewhat with social status, but in an uninteresting way
Sexual behavior and aggression can increase testosterone levels
Increasing someone's testosterone by 30% may have little to no effect on their behavior
Early developmental exposure to testosterone has more significant effects on brain circuits and later behavior

Estrogen and Health (32:32)

Dr. Sapolsky explains the numerous beneficial effects of estrogen:

Enhances cognition
Stimulates neurogenesis in the hippocampus
Increases glucose and oxygen delivery to the brain
Protects against dementia
Decreases inflammatory oxidative damage to blood vessels
Protects against cardiovascular disease

However, he notes that timing is critical for estrogen replacement therapy. Starting too late after menopause can lead to negative health effects.

Stress Mitigation Techniques (42:15)

Dr. Sapolsky discusses key factors in mitigating stress:

Sense of control - Having a sense of control makes stressors less stressful
Predictability - Being able to predict when stressors will occur reduces their impact
Outlets for frustration - Having ways to release stress is protective
Social support - Strong social connections help buffer against stress

However, he cautions that these factors are complex. For example, a sense of control is only beneficial for mild to moderate stressors. For major stressors, it can increase distress.

He emphasizes that stress management techniques must be:

Personally enjoyable - If you hate meditating, it won't help you
Practiced regularly - Can't save them just for stressful moments
Given adequate time - Need to dedicate 20-30 minutes regularly

Perception and Stress Response (56:31)

Dr. Huberman and Dr. Sapolsky discuss how our perception of events dramatically impacts our physiological stress response:

Simply deciding your wellbeing is important enough to take time for stress management can have significant benefits
How we interpret events (as challenges vs threats) shapes our biological response
There are huge individual differences in what people find stressful vs stimulating

"For some people, the perfect stimulatory amount of stress is like getting up early for an Audubon bird watching walk next Sunday morning. And for somebody else, it's signing up to be like a mercenary in Yemen."

Free Will (1:13:17)

Dr. Sapolsky argues that we do not have free will in the traditional sense:

Our behaviors and choices are the result of countless biological and environmental factors outside our control
These factors are all intertwined and cannot be separated
There is no space for a concept of free will that is "in your brain, but not of your brain"

However, he emphasizes this does not mean change is impossible:

We can be changed by circumstances and new knowledge
Understanding that change is possible can itself change our brain
This understanding makes us more open to positive influences and inspiration

Knowledge as a Tool for Change (1:20:50)

Dr. Sapolsky emphasizes the power of knowledge itself in changing our brains and behaviors:

Learning about neuroplasticity and the potential for change alters our brain
This knowledge makes us more receptive to positive information and less discouraged by setbacks
"The knowledge of the knowledge is an effector in and of itself"

Dr. Sapolsky's Upcoming Book on Free Will (1:23:44)

Dr. Sapolsky discusses his in-progress book "Determined: The Science of Life Without Free Will":

First half argues against traditional notions of free will based on current scientific understanding
Second half explores how to function in daily life with this understanding
Acknowledges it will be extremely challenging to truly internalize a lack of free will
But argues we've successfully removed notions of agency from other realms in the past (e.g. mental illness)
Ultimately believes this understanding can lead to a more humane society

Conclusion

This wide-ranging conversation between Dr. Huberman and Dr. Sapolsky covers complex topics in neuroscience, endocrinology, and philosophy. Key themes include the nuanced effects of hormones like testosterone and estrogen, the importance of individual differences in stress response and mitigation, and how our perceptions shape our biology. Dr. Sapolsky challenges common notions of free will while still emphasizing the potential for positive change through increased understanding of our biology. The discussion highlights how scientific knowledge itself can be a powerful tool for altering our brains and behaviors in beneficial ways.