Mental illness and its complications are the primary focus of Lord’s When We Collided. While the book proclaims itself as a love story, it is, more accurately, a story about different characters dealing with mental illness in either themselves or their family. Numerous characters in the novel have experience with mental health: Vivi has been diagnosed with bipolar disorder, Felix’s son Diego has depression, Mrs. Daniels’s grief has morphed into depression, and Vivi struggles with self-harm.

The novel contends with how difficult it is to speak about mental health and how daunting it is to get help. Despite how close Vivi is with Jonah, for example, she finds herself at a loss for words and struggles to describe her disorder to him:“I wish I could explain everything to Jonah. But bipolar disorder is an untranslatable term […] bipolar disorder is so complex, and it’s mine. My feelings have back rooms and trapdoors, and I’m still learning them” (223). Although Vivi has comparisons she can give to Jonah to help him better understand the diagnosis, she is unable to do so. Bipolar disorder, just like other mental health diagnoses, is not only “so complex” but also different from individual to individual.