The root could be fear and a lack of belief in Divine Providence, or the feeling of abandonment, which can also be healed by prayer and deliverance.
What Father Ripperger notes in some of his talks is that psychologists ignore the soul, and, therefore, cannot really treat or heal their patients in the majority of cases.
A friend of mine in another state brought up this sin today as she wanted to know the root cause of this after a situation which came up in her life. She wanted to know the spiritual background of certain personality disorders. I referred her to Father Ripperger's book, which I have already recommended on this blog last year. Here is the link to buy his book. But, a person cannot make decisions about another person without consulting a Catholic Thomist psychologist. One can deal with one's own problems through prayer, reading, counseling, study, and reflection.
The modern mind cannot comprehend that the seven deadly sins lead even to gross mental illness in some cases. Are there illnesses which can cause hoarding? Yes, but most problems come from the soul and the neglect of the intellect, rather than a mental problem.
Here is a list of symptoms from a mental health website. If you have family members who are hoarders, be patient, but work through the problems as much as you can from the aspect of the soul. Pray for them first of all, and then, study what Father Ripperger has to say about such things.
The great news is that people are delivered and healed through the proper means, (not charismatic,) of such sins. Praise God! Sin can be repented of and healed. So, this view should be good news.
Someone who hoards may exhibit the following: