We spend vast amounts of time and personal energy trying to calculate the most urgent threats posed by climate change. Washington, D.C. psychiatrist and climate activist Lise Van Susteren, however, says the most insidious danger may already be upon us. She’s not talking about heat, drought, floods, severe storms, or rising seas. She’s focused on the psychological risks posed by global warming.

Van Susteren has co-authored a report on the psychological effects of climate change that predicts Americans will suffer “depressive and anxiety disorders, post-traumatic stress disorders, substance abuse, suicides, and widespread outbreaks of violence,” in the face of rising temperatures, extreme weather, and scarce resources. Van Susteren and her co-author Kevin Coyle write that counselors and first responders “are not even close to being prepared to handle the scale and intensity of impacts that will arise from the harsher conditions and disasters that global warming will unleash.”

There is currently no organized discipline for the study of the psychological risks of climate change, yet it is already taking a toll on many people who tackle this issue. Surprisingly susceptible are those who might seem to be immune.

“The climate deniers? I always say they‘re really too stressed to hear the truth,” said Van Susteren. “We see this kind of thing in my work all the time, where people who aren’t ready to hear the truth about something will simply say it doesn’t exist.”

Those who do acknowledge the problem face a different set of issues, particularly those who work on the problem. Lisa Van Susteren coined the term “pre-traumatic stress disorder” to describe the grief, anger, and anxiety clinging to the scientists and advocates whose job it is to gaze into a future that can look increasingly bleak.

The longtime counselor is profoundly empathetic, and her interest in pre-traumatic stress is intensely personal. Said Van Susteren, “Pre-traumatic stress disorder? It’s what I see. It’s what I live. It’s what I see others living.” Scientists and advocates suffering from pre-traumatic stress disorder, she explained, face frequent, intrusive thoughts about the future. “In the worst of cases, it sends them into a feeling of despair,” said Van Susteren. Those battling pre-traumatic stress have accepted the truth about climate change, but rather than turning to a coping mechanism like denial, they have soldiered on, and they have paid for it with grief, sadness, and worry.

Exacerbating the problem are the piles of research telling climate crusaders to lay off the apocalyptic rhetoric, meaning that, in order to be effective communicators, experts must often stifle their most dire predictions. The problem is that climate change threatens feelings of self-efficacy — the sense that we can control our destiny. This is precisely why social scientists urge communicators not to overburden the public with catastrophic predictions about the future, because doing so can inspire fatalism.

Van Susteren offers guidance for coping with climate-induced anxiety. Take care of yourself, she says. Sleep. Exercise. Nurture relationships with friends and family. Laugh, dance, and play games. But most of all, she says, do something. Climate action can make for powerful medicine. It can restore self-efficacy and banish fear and fatalism. Granted, said Van Susteren, “you still need to have a strong stomach and a certain resiliency to want to go down into the trenches.” But that way lies hope, community and a shared sense of purpose.

The psychiatrist has taken a healthy dose of her own medicine. She helped to organize a rally for climate justice on the National Mall while Pope Francis addressed a joint session of Congress. The rally was the work of Moral Action on Climate, a coalition of social justice, environmental, and faith organizations. Said Van Susteren, “The faith tradition is bringing this incredible sense of the moral grounding in what we’re doing.” Organizers are preparing to host tens of thousands of demonstrators.

Van Susteren says that she is hardly sleeping these days; her commitment to the rally has consumed all of her time. Her cell phone buzzes unremittingly, even during interviews, prompting the psychiatrist to roll her eyes and silence the device with a forceful tap. But her fatigue and frustration are side-effects of a potent remedy. She is treating her fear about the future with the best medicine around.

She’s taking action, and she’s not alone. Together, activists are reaffirming a mastery of their fate. Said Van Susteren, “Together we can do what needs to be done.”