Which of the following statements pertaining to asthma is false?
a. Parental and interpersonal conflicts have been tied to the development of asthma.
b. Asthma sufferers can experience asthma-like symptoms simply by believing that an inert substance they breathe will lead to airway obstruction.
c. Asthma has been shown to be linked to periods of depression.
d. Rates of asthma have decreased considerably since 2000.