When it comes to psychological functioning, we can discuss a broad spectrum of psychology. What we mean by functioning is our ability to process the environment with minimal distortions. Distortions come in the form of hallucinations, projecting our emotions onto others, or unconsciously coercing people to engage with us so that we can act out our traumas and conflicts using something called projective identification. No one functions without problems popping up from time-time and that's okay. We're all human. I'll get back to that, but first I'll describe functioning at the other end of the spectrum.
Psychosis
Psychosis is at the far end of psychological functioning. It's very sad to see. When people believe that if they use the toaster, they might make something bad happen to their family and so take it and drive 50 miles to a garbage dumpster behind a Walmart, that's an example of someone under psychosis. I've worked with people with psychosis and they can be very nice people. Usually, their psychosis hurts themselves more than others. The brother Ben, on Ozark, is an example of someone suffering from psychosis. Note that psychosis is different than being a psychopath, which is a personality classification, not a description of functioning. You can be psychotic and not a psychopath, or neurotic and a psychopath, and so forth. I'm not going to get into personality in this post because it's a much bigger topic.
Neurosis
Neurosis is at the healthier end of the spectrum. We're all a bit neurotic. When we're standing in front of the mirror stressed out about how we look and judging ourselves, that's being neurotic. We aren't able to just see the person in the mirror; we're seeing all of our judgments and ideas about how society will judge us and that's distorting what is really there. Being neurotic usually doesn't have much of an impact on people's lives or interpersonal relationships. Since neurosis is so common, it can be applied to most of the characters in Ozark.
Borderline
And then there's borderline functioning. This level of psychological functioning means the "borderline" between neurotic and psychotic. While everyone is neurotic from time to time (or all the time), and few people are psychotic, a fair number of people are borderline. Being in a relationship with someone with borderline functioning will be a painful experience because they tend to swing back and forth between idealizing the relationship and devaluing it. It can mean one day they love you more than anything and the next day they hate you more than anything. And you have no control over what triggers them. If this sounds like a four-year-old, that's because it's a similar level of functioning.
To illustrate, you might be engaging in a casual conversation with someone else and the person with borderline functioning is likely to project all of their psychological fractures onto the conversation and then later attack you for all of the horrible things you've done. It can feel like you actually did something wrong since borderline functioning people can be very good at gas-lighting. It's a survival adaptation after all and they've relied upon it most of their lives.
Darlene in Ozark is a great example of someone with a borderline level of functioning. She is also a psychopath. A psychopath with borderline level of functioning makes for a great TV show character, but also makes for a very difficult human being.
How do people with psychosis differ from those with borderline functioning?
People with psychosis such as might be experienced in a manic episode, hurt people indirectly because the behavior is so harmful to themselves. However, generally, the object of anger in people who are under psychosis isn't like it is with people with borderline functioning. It's very common for borderline functioning people to make the people closest to the them the object of their anger. This is where it gets more complicated but I'll try to explain it. Borderline functioning people don't lose touch with their ego, but they do lose touch with objective reality. As a result, they take things very personally. Psychotic people not only lose touch with objective reality, but they also lose touch with their ego. There is no person inside to take something personally. That's why it's easier to have sympathy for the psychotic person rather than the borderline functioning person. Borderline functioning people retain their sense of self but project all of their hurt onto the people around them and then treat those people as if they are the source of the hurt rather than recognizing it is a projection of themselves.
Conclusion
This is only touching the surface of psychological functioning, but I thought it would be useful for those who aren't familiar with this spectrum to understand a little bit more about it.