The most common effects of marijuana are relaxation, euphoria, and improved mood. Less common effects include increased anxiety, paranoia, and psychosis. Short-term effects of marijuana also include impaired short-term memory and decreased ability to concentrate, slowed reaction time, impaired motor skills, and increased heart rate. Long-term effects of marijuana are similar to the short-term effects on a more chronic level. For example, regular users of marijuana may experience difficulty with problem solving and critical thinking as well as reduced IQ over time. Some studies suggest that there is an increased risk for developing bronchitis or other respiratory infections in people who smoke marijuana regularly.