Which of the following is NOT an effect of caffeine?

Caffeine is a central nervous system stimulant that primarily produces effects such as increased alertness, enhanced energy, and improved mood. Its stimulatory properties often lead individuals to experience heightened stimulation and focus, which can also contribute to feelings of hyperactivity.

When considering headaches, it’s important to note that caffeine withdrawal can indeed lead to headaches, as individuals who consume caffeine regularly may develop a dependency. When they abruptly reduce their intake, they may experience withdrawal symptoms including headaches.

Increased fatigue, however, is not a typical effect associated with caffeine consumption. Instead, caffeine is generally consumed to combat fatigue and increase wakefulness. Therefore, stating that increased fatigue is an effect of caffeine does not align with its well-documented primary effects on the human body. This makes 'increased fatigue' the correct choice as it does not reflect the typical impacts of caffeine consumption.