Ecstasy/MDMA and other stimulants like speed and cocaine
Combining MDMA with uppers mainly ensures that you notice less of the MDMA. The desired effects, such as euphoria, are smoothed out. So you feel less of the MDMA. There is a chance that you will then take more MDMA to get a bit more effect. The uppers also remove the vagueness of the MDMA. You feel a little brighter.
The more MDMA you take and if you combine it with other uppers, the bigger the hangover. You feel empty and exhausted.
The combination also causes more brain damage. And a greater load on the heart and blood vessels.