"With people that suffer from mental illnesses, if you remove one aspect of thinking, it will need to be replaced by another,"
Mental conditions have many aspects to them. In EFT language, an aspect is another branch of the condition or the problem. EFT is used with other psychotherapies to produce effective results. Dr.D Feinstein talks about the effects of EFT in his book Energy Psychology.
As with some mental conditions, including addictions and cravings, Gary Craig calls these addictions as tranquillizers. So the huge question becomes - what are they tranquillizing from? It is the same with dieting and weight gain!
If you remove an addiction without finding what caused that addiction in the first place, then, the addiction will return in another form because the underlying anxiety was not addressed. Example: Someone works on controlling an alcohol addiction - is he successful if he replaces alcohol with smoking? So Now when he is anxious, he smokes instead of drinking beer? Looked like he has substituted one addiction for another. Below is an article written by a EFT practitioner on the different aspects of the smoking addiction.
EFT does take some effort, much persistence but the rewards appear to be long term.