To avoid using my time to reinvent the wheel, I found this graphic by York University showing some of the systems of oppression. I like how they present an overlap of systems because many of us are impacted by more than one. They created a post that provides well-researched and nuanced definitions, which can be found here.
More informally, I have worked with the following categories as I think about the systems that are harmful to my clients and communities:
White Supremacy and White Normativity
Heteronormativity and Heterosexism
Patriarchy and Sexism
Cis-normativity and Transphobia
Ableism
Other systems relevant to you (education, religion, etc.)
Each system uses itself as the norm of personhood and frames those outside their system as less than or other.
Anyone outside of these systems experiences harm as an outsider. While there is an element of not belonging that is painful enough, these systems are often covertly implemented into our education, media, laws, and socialization. The power structures don't value variety; a hierarchy places marginalized people in uncomfortable and dangerous positions. Examples include the epidemics of police brutality against Black people, taking away the human rights of the LGBTQIA+ communities, lack of structure around a mass disabling event like COVID, and unjust and inhumane immigration policies.
I believe that systems of oppression are very much connected to our mental health. Neglecting conversations around oppression do a disservice to the client and the therapeutic process. Sometimes symptoms can be misunderstood without proper context (is a person pathologically paranoid, or did they grow up surveilled in the education system and their community?). Often, layers of identity overlap with people's experiences of depression, anxiety, and trauma.
I remember going to therapy as a client and getting my clinical symptoms of depression resolved but knowing that we wouldn't get to the core of it without talking through my racial identity and the complex ways I experienced oppression and privilege. I wanted to bring this up, but I was nervous. When my therapist assumed I was better and recommended reducing our sessions because I was more functional, I left therapy prematurely. This was a big part of my motivation to frame my practice this way. And that was over a decade ago.
Today it is more important than ever to acknowledge how systems of oppression impact us. Often when I work with clients, they come in with the idea that something is wrong with them. But when we get into the contexts of oppressive systems, I observe a weight lifted off of them as we normalize why it would be depressing, anxiety-provoking, and traumatic to operate within these systems as a marginalized person.