The Science Behind “Overthinking”

It is late, the lights are off, and your mind is replaying a conversation from lunch. Did that comment sound rude? Why did you say it like that? What will they think tomorrow? An hour later you have not solved anything, but you are wide awake and feel worse than when you started.

Most people call this overthinking. It is a familiar experience, but it is not a medical diagnosis, and scientists rarely use the word. Instead, researchers study a family of related habits of mind that they call repetitive thought. Looking at that research helps explain why some kinds of thinking go in circles while others actually help.

What researchers mean instead

One major review defines repetitive thought as the process of thinking attentively, repetitively or frequently about one’s self and one’s world. That broad category includes worry, rumination, mental rehearsal, reflection and problem solving, among others.

Two forms come closest to what people mean by overthinking:

• Rumination usually means dwelling on what has already happened, especially on why you feel bad. A common questionnaire asks how often, when sad, people think things like “Why do I always react this way?”
• Worry looks forward. It has been described as an attempt to engage in mental problem-solving on an issue whose outcome is uncertain but contains the possibility of one or more negative outcomes.

Importantly, repetitive thought is not always harmful. The same review lists constructive consequences, including recovery from upsetting events, adaptive preparation and planning, and uptake of health-promoting behaviors. Worry, too, is proposed to have useful functions when it is objective, controllable, and brief, such as pointing your attention toward a problem that needs dealing with.

Why and how: the difference that seems to matter

If thinking hard about a problem can help, why does overthinking so often feel useless? One answer researchers have proposed concerns the style of thinking, not just the amount. Repetitive thought can be abstract (“Why does this always happen to me? What does it say about me?”) or concrete (“What exactly happened, and what could I do next?”).

Experiments have tested this directly. In one, people who had recovered from depression were prompted to think about causes and meanings, with questions like “Why did this problem happen?”, and their social problem solving was impaired. In currently depressed patients, prompts focused on the concrete process of how to proceed reduced the problem-solving difficulty usually seen in that group. In another study, after watching a distressing film, abstract rumination resulted in slower recovery from negative affect than did concrete rumination or distraction.

There is also an important condition. In many lab studies, people spend about 8 minutes either ruminating or imagining neutral scenes unrelated to themselves, and rumination tends to worsen mood and thinking. But these differences are found only when participants are already in a dysphoric mood, meaning low or unhappy. This suggests that rumination is not harmful in itself so much as it amplifies a bad mood that is already there.

When overthinking links to bigger problems

Rumination has drawn attention because it is connected to more than one kind of distress. In two longitudinal studies, one of 1,065 adolescents and one of 1,317 adults, rumination statistically accounted for the link between symptoms of depression and anxiety, fully in the adolescents and partly in the adults. In the adolescent sample, rumination fully mediated the association between baseline depressive symptoms and later increases in anxiety. These are statistical patterns in questionnaire data, so they are consistent with rumination playing a role, but they cannot prove it is the cause.

A more recent review describes rumination as a transdiagnostic vulnerability, meaning a risk factor shared across several conditions, including anxiety, depression, psychosis, insomnia, and impulsive behaviors. Its authors propose that rumination can become a learned habit, especially in the context of poor executive control and negative information-processing biases. If that model is right, part of the reason overthinking feels automatic is that, like any habit, it has been practiced many times.

What the brain may be doing

Brain research on rumination has focused on the default mode network, a set of regions that tends to be active when we are not focused on the outside world, such as when we daydream, remember the past or think about ourselves.

A 2020 meta-analysis noted that findings have been inconsistent across individual studies. Pooling 14 fMRI studies comprising 286 healthy participants, it found that rumination tasks were associated with activity in the default mode network’s core regions and its dorsal medial prefrontal cortex subsystem.

Research on depression adds another piece. A review of meta-analytic findings reported reliably increased functional connectivity between the default mode network and the subgenual prefrontal cortex, a region linked to mood, and this connectivity often predicts levels of depressive rumination. Interestingly, the same authors found no reliable abnormality in blood flow in the default mode network’s own nodes in depression, even though blood flow in the subgenual prefrontal cortex was reliably increased. Their interpretation is that rumination may arise when self-focused thinking becomes tightly linked with emotionally heavy, withdrawal-related processing. That is a model, not a settled fact.

What is still uncertain

“Overthinking” covers many different experiences, from replaying an awkward moment to worrying about exams, and research on rumination and worry may not capture all of them. Much of the evidence comes from questionnaires and short lab tasks, and the brain-imaging results are correlational and, by the researchers’ own account, have been inconsistent. Scientists also still debate how best to separate harmful rumination from healthy reflection, since both involve thinking repeatedly about yourself. Treatments aimed at rumination exist, but the review above describes the trials as preliminary.

The takeaway

Thinking about a problem over and over is not automatically bad. Research suggests it tends to help when it is brief, concrete and aimed at what to do next, and to hurt when it is abstract, focused on “why,” and fueled by a low mood. Brain studies point to self-focused networks, especially the default mode network, though the picture is still being worked out. The experiments above suggest that shifting from “why is this happening?” to “how could I handle this next?” may make repetitive thinking more constructive, although this has mostly been tested in short lab tasks. If repetitive worry or low mood is persistent or getting in the way of daily life, talking to a doctor, school counselor or qualified mental health professional is a sensible step.