Which of these statements is true?

A) Placebo effects can influence both psychological and physical disorders.
B) Valuable research is done by people outside the scientific community, but scientists try to discount the importance of this research.
C) Scientific breakthroughs happen every day.
D) Experimental rather than observational research is required to learn about patterns of disease.

Placebo effects have been shown to have an impact on both psychological and physical conditions. For example, placebos have been found to reduce pain perception, improve symptoms of depression and anxiety, and even boost immune system response. Therefore, statement (A) is true. Statement (B) is largely false, as scientists often rely on research and insights from individuals outside the scientific community. Statement (C) is an exaggeration, as scientific breakthroughs are relatively rare events. Finally, statement (D) is not entirely accurate, as both experimental and observational research can be used to learn about patterns of disease.