Roughly 8.7 million Brits take antidepressants and around 50 million beta blocker prescriptions are handed out annually, often for anxiety and heart conditions. But taken together, the drugs could increase the risk of dangerously low blood pressure and abnormally slow heart rates, data shows. The research found that combining the two types of drugs could lower blood pressure by up to 20% and raise the risk of a slow heart rate by 25%. CYP2D6 is an enzyme that helps break down beta blockers but SSRIs could hinder that process, the research found. Low blood pressure can cause everything from dizziness to organ failure, and a low heart rate can cause cardiac arrest.