It is the softest word in the jury charge and the hardest to prove. It sounds like a feeling. It is an event in the body.
The charge asks the jury to compensate mental anguish, and the defense treats the phrase like weather. Sad things happened, they say, and sadness is not an injury. That argument only works if mental anguish is a mood. It is not. After a serious injury the brain and the nervous system change in ways that can be measured, and the measurements move in the same direction the suffering does.
Start with a protein the brain uses to keep its own wiring alive. It is called brain-derived neurotrophic factor, and its job is to help brain cells grow, connect, and repair. In people who are depressed, the amount of it circulating in the blood runs low, and when the depression lifts the level climbs back toward normal. That is not a metaphor for feeling low. It is a biological marker that tracks the state of the person. A jury told that a plaintiff is merely sad is being asked to ignore a chemistry that rises and falls with the injury.
Then look at the nerve that is supposed to bring the body back down. The vagus nerve is the brake on the stress response, the wiring that slows the heart and settles the system after a threat has passed. You can measure how well that brake works by looking at the tiny beat-to-beat variation in the heartbeat, a number called heart rate variability. In people carrying post-traumatic stress, that variation is reduced. The brake is worn. The body has trouble getting back to rest, which is another way of saying the alarm never fully turns off.
Put those two together and mental anguish stops being a soft word. A low marker of brain repair and a worn recovery brake are not sadness. They are the fingerprints of an injury that happens to live in tissue a camera does not photograph. The plaintiff is not weak and is not exaggerating. The plaintiff is running a nervous system that took a hit and has not reset.
Here is the lawyering. Stop apologizing for the mental-anguish element. Stop treating it as the soft part of the case you hurry past to get to the broken bones. It is anchored in biology as real as the fracture, and the science that anchors it is old, replicated, and boring in the best way. At the charge conference, own the word. Mental anguish is not the jury being generous. It is the jury being accurate.
The biology of mental anguish rests on peer-reviewed meta-analyses. On reduced serum brain-derived neurotrophic factor in depression, which rises toward normal with antidepressant treatment, see M. Sen, R.S. Duman & G. Sanacora, Serum Brain-Derived Neurotrophic Factor, Depression, and Antidepressant Medications, Biological Psychiatry (2008). On reduced resting heart rate variability in post-traumatic stress, see X. Ge et al., Posttraumatic Stress Disorder and Alterations in Resting Heart Rate Variability, a systematic review and meta-analysis (2020). This is general information, not legal advice.
