In order to answer your question, we must first define the word – causes, and then see if that is the correct term to explain why people use substances heavily. In Chapter 5 of The Freedom Model for Addictions, the authors make the distinction between causes and reasons for one’s substance use:

“There is a fatal flaw in the practice of trying to understand the “causes” of human behavior in the same way that we understand the causes of an apple falling from a tree or some other purely physical phenomenon. The flaw is that people are equated with unconscious things when analyzed this way. But there’s an important difference between people and unconscious things: consciousness. People have something nonphysical that guides their behavior; they have thoughts, ideas, beliefs, goals, and intentions. Most simply put, people have reasons in their minds for behaving the way they do. Unconscious objects have no such ability. This distinction between people and things is crucially important. The movement of things is caused by other things acting upon them; the behavior of people is chosen by themselves for various reasons.”

So the authors determined that people are not caused to use substances, but rather have personal reasons for their use. Further on in the chapter it goes on to say:

“There’s good reason to parse this out. We hear endless talk about “the causes of addiction,” as if people are the same as lifeless, mindless objects without the power of choice. “Cause” is a strong word that evokes simple cause-and-effect relationships devoid of choice, and the psychological establishment has used it in this exact sense throughout the 20th century.”

And then later, it continues with:

“We need to make a note about “psychological causes of addiction” to be clear about what our stance is. Heavy substance use is absolutely a matter of psychology; people want it and choose to do it because of how they think. It is a matter of the mind and thus psychological. The Freedom Model stance is that people are free to choose to think differently and doing so will change the way they feel and behave, so in that sense, substance use is a matter of psychology. However, when treatment professionals speak of psychological causes, they are referring to mental disorders or diseases, which they believe to be out of your control and the cause of your substance use.”

And so The Freedom Model stance is that the individual chooses their substance use patterns based on their natural and self-evident ability to think with their mind, and base those decisions on their reasoning power (their “reasons for use”). In other words, no one is CAUSED to use substances, they have REASONS for using substances. And reasons are changeable and chosen by the individual, while causes are out of the direct realm of control of the individual.