Please note all UI is placeholder.
So here are the beginnings of the character stats. Hunger and fatigue obviously rise while you’re milling about. Fatigue will rise faster as you exert yourself. If they get into the red then you’re going to start to suffer physically, but also mentally. So you need to keep up on your sleep and food to keep yourself in the right frame of mind necessary to survive.
You see above you have stress and morale. Stress is the short term stressed effect of seeing zombies close by, hearing banging at your door or other unsettling noises, and generally anything which stresses you out (which will likely include annoying companions in the future). If nothing is stressing you out your stress level begins to drop. However, while you are stressed it will start dragging your morale down, which is a more long term effect and harder to change.Stress can be lowered by killing zombies, drinking booze, taking some pills, or as the screenshot’s tooltip shows, a cigarette to calm the nerves.
Of course, all these things are addictive, so rely on them too much and you will suffer withdrawls if you go without them, which will only drag your emotional state further into the gutter.
There will be more stats than this, though. Coming next is sanity, which will result from high stress and low morale for long periods, and will be an even more long term effect that’s nigh on impossible to rectify if it drops.