Have you ever stayed awake at 3 a.m., replaying a conversation from earlier that day, wondering if you said something wrong? Or maybe you’ve spent hours planning for every worst-case scenario, only to end up doing absolutely nothing?
“We have anxious thoughts because the brain is trying to keep us alive. To the brain, survival is much more important than happiness. So, the brain often conjures up worst case scenarios and “what ifs”, so that we can prepare for disaster. The trouble is, the brain regularly gets it wrong,” Dr. Lucy Russell, Clinical Psychologist emphasizes in her article.
That is overthinking—what most people now describe as a “freeze in thought,” and it might just be your brain’s outdated way of trying to protect you.
From saber-toothed cats to spreadsheet panic attacks
The fight-flight-freeze response is an automatic reaction to danger. In prehistoric times, it helped us survive life-threatening situations. When triggered, the body speeds up heart rate and breathing, tenses muscles, and prepares to fight, flee, or freeze.
But today’s “threats” are different. We’re not being chased by predators anymore, but we do face deadlines, relationship issues, financial worries, and social anxiety. According to GoodRx and Healthline, modern stressors like traffic jams or arguments with partners can still trigger those same primal responses.
A lesser-known aspect of this reaction—the freeze—can also occur in our thoughts. Instead of fighting or running away, we get stuck in cycles of “what ifs?” and “should haves.” That’s overthinking.
The brain’s smoke alarm on overdrive
Overthinking is more than just a bad habit. It’s a mental defense mechanism that has gone wrong. According to LifeMD, it’s a repetitive and unproductive cycle where we replay mistakes, worry about uncertainties, or imagine worst-case scenarios.
From an evolutionary perspective, this behavior made sense. Our ancestors had to think ahead to avoid dangers. However, our brains today act like overly sensitive smoke detectors, constantly searching for potential threats even when there are none. Psychologist Susan Nolen-Hoeksema found that almost 73% of adults aged 25 to 35 deal with daily overthinking.
This habit isn’t just annoying; it’s harmful. Brain imaging studies mentioned by Practo show that overthinkers display increased activity in the prefrontal cortex, leading to decision paralysis, in the amygdala, resulting in anxiety, and in the Default Mode Network, causing excessive self-focus.
Overthinking is also connected to cognitive distortions such as catastrophizing, perfectionism, and black-and-white thinking.
When thoughts become traps
Let’s be clear: overthinking isn’t a clinical diagnosis, but its effects are very real. The Oxford Research Encyclopedia of Psychology explains that worry and rumination increase the risk of anxiety, depression, eating disorders, and even non-suicidal self-injury.
A 2013 study by Nolen-Hoeksema found that rumination can predict how long depressive episodes last.
The physical effects are just as serious. Studies by BetterHelp, Onebright, and GoodRX show that chronic overthinking can cause sleep problems, fatigue, headaches, muscle tension, digestive issues, high blood pressure, and a weakened immune system.
It also disrupts your everyday life. It can lead to procrastination, social withdrawal, decision fatigue, and poor performance at work or school.
What can we do about it?
Luckily, we’re not stuck in this freeze forever. Mindfulness-Based Cognitive Therapy (MBCT), breathing techniques, and grounding exercises can reduce rumination and calm the stress response. CBT (Cognitive Behavioral Therapy) is also a way to challenge unhelpful thoughts and motivate action.
Sometimes, the solution to overthinking is simple: movement. According to the Mental Health Foundation, activity lowers stress hormones and boosts mood-enhancing endorphins. Even taking small, imperfect steps, like writing a draft, sending a message, or making a call, can help break the paralysis.
When it feels like too much, seek help. Mental health professionals are trained to help rewire these thought loops.
Overthinking is the brain’s way of trying to protect you. But what once saved us from lions now keeps us stuck in worry. Today, survival doesn’t mean scanning for threats—it means learning when to pause, breathe, and choose clarity over chaos.
You don’t have to fight or flee—you don’t have to freeze in thought, either.
