Smiling or laughing while disclosing painful experiences is not an uncommon phenomenon, and it can serve different functions.  It’s important to process the deeper intention and the unspoken communication that often lies beneath the surface when affect doesn’t match content. Emotions that are in sync with the experience allows for authentic processing and compassionate witnessing so genuine healing can take place.  Here are some possible reasons why there is a disconnect between content and emotion:

Smiling when discussing trauma is a way to minimize the experience.
It communicates that what happened “wasn’t so bad.” Downplaying the severity is a common strategy that trauma survivors use when trying to maintain a connection to caretakers who betrayed or violated them.

Laughter can protect clients from feeling the depth of their actual pain.
Many survivors believe if they don't laugh about their experiences they will connect to intense feelings of rage, despair, disappointment, or sadness that will flood or overwhelm them.  Feeling deeply is often associated with a loss of control. Laughter keeps the pain at arm’s length.

Smiling or laughing when disclosing trauma can be an indicator of shame.
Some trauma survivors hold deeply entrenched feelings of self-blame and other distorted and inaccurate thoughts about the role they believe they played in their abuse. Laughter can communicate that shame while also short circuiting any further exploration of their trauma experiences.

Smiling or laughing when disclosing trauma can be information about family of origin experiences.
The inability to access or express specific emotions in adulthood may be the inevitable byproduct of either having feelings trivialized, learning that emotional expression was unsafe, or not having those emotions modeled and normalized in childhood.

Smiling is a way to fend off compassion or empathy from a therapist.
When clients disclose something painful without the appropriate affect, this can be a conscious or unconscious attempt to stave off compassionate responses that feel unfamiliar and uncomfortable. Kind words can be misconstrued as “pity,” create suspicion about therapists’ “real” motives, or leave clients feeling too vulnerable.

Laughing says their trauma is not important because they aren’t important.
Some survivors use laughter to deflect from their experiences because they don't feel worthy of the attention.  Their pain doesn't matter. Many survivors don't have enough ego-strength or self-esteem to believe they deserve guidance, support, and validation.

Smiling communicates they don't have the tools to manage “negative” emotions.
Many clients believe if their feelings come to the surface they won't know how to effectively navigate and titrate them.  Smiling is a creative coping strategy that unconsciously paces the work.  It’s also an important indicator that more resources for affect regulation need to be installed.

Smiling is a way to “protect” therapists.
Some clients feel protective of their therapists’ feelings and worry that sharing their trauma might overwhelm, frighten, or disgust their therapist.  Laughing while recounting something painful says, “I’m ok, you don’t have to take care of me.” Instead, clients are attempting to take care of their therapists.