You'll notice that many human disorders/diseases share the same symptoms. Anxiety can have racing thoughts and so can Bipolar. Hallucinations can happen from sleep deprivation, schizophrenia or even from a bacterial infection of the brain (Neurosyphilis).
If you break your human self down into it's most essential components you'll find that a lot of people above simply mentioned certain components being disturbed but the way or reason they were disturbed may be unique to them.
Your emotional self (fear, sadness, concern, worry etc)
Your mental self (thoughts manifest here/sometimes delusions)
Your physical self (racing heart, chest pain, nervous legs, digestive system etc)
Your predisposition (genetics etc and how you are unique and affected in different ways, gifts/talents, your sensitivities etc)
Your ability as a human to experience unseen realities (hallucinations, jinn harassment, dreams)
Psychiatry gets people more confused sometimes. It has huge benefits sometimes (people used to die from bipolar). The point is to always keep it simple and not isolate problems this great creature the human being can have to just a single component or sub-component.
I've seen someone get diagnosed with bipolar after a stressful period in their life but they don't have it in their genetics at all and the person didn't have any issues before that.