The sudden, visceral feeling known as a “stomach drop” is a common, powerful, and involuntary physical response that occurs regardless of how long the relationship has been over. This sensation confirms that the brain and body register the sight of your ex not as a casual event but as a sudden emotional trigger. Understanding this reaction requires separating the physical survival mechanism from the psychological residue of the former attachment. This physical alarm system highlights the profound connection forged in a romantic partnership.
Why Your Body Reacts: The Fight or Flight Response
The sinking feeling in the abdomen is the physical manifestation of your sympathetic nervous system activating the fight-or-flight response. This reaction is triggered when your brain’s emotional centers perceive the encounter as a threat, flooding the bloodstream with stress hormones like adrenaline and cortisol.
The surge of adrenaline and cortisol causes the body to prepare for emergency action by redirecting resources. Blood flow is diverted away from non-essential systems, including the digestive tract, and shunted toward the large muscles and the brain. This temporary suppression of digestive activity creates the sensation of hollowness or sinking in the stomach, which the brain perceives as a physical drop.
This communication between the brain and the abdomen is facilitated by the vagus nerve, the main component of the gut-brain axis. The vagus nerve transmits the emotional distress signal from the brain to the enteric nervous system, the “second brain” in the gut, almost instantaneously. This neural pathway ensures that the emotional shock bypasses rational thought and presents as a physical symptom, making the reaction feel out of your control.
The Residue of Attachment and Memory
The ex-partner acts as a conditioned trigger because the brain encoded the relationship using neurochemical rewards associated with survival and bonding. Romantic love activates the same dopamine-driven reward circuitry as addiction cravings, creating a persistent neural network. Seeing the person instantly reactivates this network, causing a rush of neurochemicals that the body interprets as an emotional shock wave.
This activation occurs in the limbic system, the brain’s emotional center, bypassing the logical processing of the prefrontal cortex. As a result, the emotional memory associated with the ex is retrieved with vividness, prompting the physical alarm before conscious thought can intervene. The intensity of this response is often amplified by lingering emotional ambivalence or unresolved grief from the breakup.
This reaction can also signal a momentary reactivation of the attachment system, regardless of the relationship’s health. For those with an anxious attachment style, the encounter can trigger a fear of abandonment, manifesting as separation anxiety. The visceral reaction is not necessarily a desire to get back together, but rather the body’s automated distress signal about the presence of a person who was once central to its emotional regulation.
How to Process the Intense Reaction
When the physical alarm sounds, the priority is to regulate the nervous system using grounding techniques. The 4-7-8 breathing method is effective, involving inhaling for four seconds, holding for seven, and exhaling slowly for eight seconds. This stimulates the vagus nerve and activates the parasympathetic “rest and digest” mode, signaling to the brain that the emergency is over and the body can return to a calmer state.
After the encounter, use cognitive reframing to challenge the emotional interpretation of the physical shock. Label the feeling as a predictable biological response—a “cortisol spike” or a “limbic system echo”—rather than a sign of longing or failure to move on. Practice sensory grounding, such as the 5-4-3-2-1 technique, by naming five things you see, four things you touch, three things you hear, two things you smell, and one thing you taste. This pulls attention away from the emotional memory and into the reality of the present moment, helping the brain recognize the trigger as a memory, not a current threat.