Yes, being stressed out can cause high blood pressure. When you are stressed, this sets off the fight or flight response. And this stress response continues until the stressor is dealt with or you find ways to cope with it. But if you don't get help for being stressed out, the stress response continues chronically, and this puts you at risk for developing high blood pressure. What happens is that when you are stressed out, then this sets off the amygdala, which in turn activates the sympathetic nervous system. When the sympathetic nervous system is set-off, it directly connects to the blood vessels and contricts most of them, and also increases the heart beat, thereby raising the blood pressure. Additionally, the sympathetic nervous system connects to the adrenal medulla to release adrenaline into the bloodstream. The adrenaline then travels throughout the body, and also functions to contrict most of the blood vessels and causes the heart to beat faster, thereby increasing blood pressure.
So when you are stressed out, it can lead to high blood pressure.