MDMA is known for causing which of the following effects?

MDMA, also known as ecstasy or molly, is primarily recognized for its stimulatory and empathogenic effects rather than simply negative reactions. While the substance can sometimes lead to side effects such as nausea or anxiety in users, the correct answer is focused on the broader profile of MDMA's effects.

MDMA is known to typically induce feelings of increased energy, emotional warmth, and enhanced sensory perception, which aligns with the choices that suggest positive experiences. However, it can also indeed cause negative reactions, including nausea and anxiety, particularly in higher doses or among inexperienced users. This means that occasional adverse effects like nausea and panic attacks may occur, but these are not the primary or hallmark effects of MDMA usage.

The other options highlight effects that are more in line with MDMA's psychoactive properties such as increased energy and clarity, intense relaxation, or improved focus. However, MDMA can also cause a disorganized thought process or distractibility, which would interfere with attention and focus, making these answers less suitable as they do not directly capture the essence of MDMA's well-documented effects. In sum, while nausea and panic attacks can be experienced, they are not the most noteworthy impacts of MDMA compared to its primary features.