• People with lower cholesterol levels are more likely to die violent deaths.
• If you put primates on a low-cholesterol diet, they become more aggressive. Lowering animals’ cholesterol seems to affect their levels of serotonin. Even fruit flies start fighting if you interfere with their serotonin levels.
• Studies have linked serotonin levels in people to violence, impulsivity, suicide, and murder.
• In a randomized controlled trial, statins were found to increase aggression in post-menopausal women though, oddly, not in men. Giving statins to Nile tilapia made them more confrontational and altered the levels of serotonin in their brains.

Paracetamol blunts physical pain by reducing activity in certain brain areas, such as the insular cortex, which plays an important role in our emotions. Paracetamol can blunt our social pain too.

Recent research has revealed that our brain's pain centers also share their home with empathy. Paracetamol significantly reduces our ability to feel positive empathy.

• Asthma medications are thought to bring on ADHD symptoms by altering levels of serotonin or inflammatory chemicals, which are thought to be involved in the development of both conditions.
• People on antidepressants do feel less depressed, but they also begin not to care about normal things that people care about.

No one is arguing that people should stop taking their medication. However, it is important for people to be informed about how the treatment might potentially change their personalities.