I was reading this write-up by Suresh Jindal which is titled "Dependent Arising: The Delusion of 'I'". I want to share this excerpt from that which talks about the "cause of suffering". Go ahead and read what I pulled out:
"The Buddha taught that the True Causes of suffering are the three poisons of attachment, aversion and ignorance. Experientitally we know that other than bodily suffering, our mental and emotional suffering results from wanting to be in an uninterrupted embrace with sensual pleasures, and an aversion and hatred for objects and beings that obstruct this hedonistic warmth. Thus we want our wealth, health, fame, name, and romantic love to last foreer, and we fly into a demented rage of anger, despair and hatred against anything and anybody who blocks this sensually pulsating pursuit.
The commonly held belief that things are permanent is a hallucination and an illusion. This ignorance of the true nature of reality is the root of delusion. This ignorance along with the aversion and attachment are the three poisons that are true cause of suffering. The afflictive emotions of anger, jealousy, pride, hatred etc. are result of our attachment to some experiences and persons and averion to others, on the assumption that they are permanent and last forever. This deluded way of perceiving reality causes the defilement and obsucarations that lead to suffering