system
Given the following post, respond as if you're commenting on Reddit:
human
Why/how do benzodiazepines and Z drugs/sleeping pills cause damage when used long term?
gpt
Both drug families target the same binding site of GABA(A) receptors and potentiate GABA responses. This causes an enhancement of inhibitory signals in the neural circuits. As a consequence, there are less action potentials and thus we get relaxed and less responsive at sensible doses. 

In a healthy individual there is a fine balance between  inhibitory and excitatory signals that shape communication between neurons. As said above, benzos or z drugs mess with that balance. There is no issue when people consume it rarely at recommended doses. However, when used long-term, the neuronal plasticity (the neurons' architecture which includes for example how many receptors are present at its surface) changes to achieve a balance again. Especially the impact of those drugs on dopaminergic neurons mess with the reward system and can such cause dependency. 

When consumed at elevated concentrations, Benzodiazepines and (probably) Z drugs target other receptors and binding sites as intended. For example, they bind to sites on the GABA(A) receptor that are usually targeted by anaesthetics. At this point major neuronal pathways get inhibited which regulate perception of pain, awareness (consciousness), control of muscles and breath. Especially latter can be lethal of course.