 Increased levels of allopregnanolone can produce paradoxical effects, including negative mood, anxiety, irritability, and aggression.This appears to be because allopregnanolone possesses biphasic, U-shaped actions at the GABAA receptor – moderate level increases (in the range of 1.5–2 nmol/L total allopregnanolone, which are approximately equivalent to luteal phase levels) inhibit the activity of the receptor, while lower and higher concentration increases stimulate it.This seems to be a common effect of many GABAA receptor positive allosteric modulators.