Depression causes persistent changes in mood, thinking, energy, and daily functioning that last at least two weeks. It goes beyond feeling sad after a bad day. The core signs include a depressed mood most of the day nearly every day, loss of interest in things you used to enjoy, changes in sleep and appetite, fatigue, difficulty concentrating, feelings of worthlessness, and in some cases, thoughts of death or suicide.
The Core Signs of Depression
A major depressive episode involves at least five specific symptoms occurring together over the same two-week period. At least one of those five has to be either a persistently depressed mood or a noticeable loss of interest or pleasure in nearly all activities. The other symptoms can come from the following list:
- Depressed mood most of the day, nearly every day. This can feel like sadness, emptiness, or hopelessness. In children and teenagers, it often shows up as irritability instead.
- Loss of interest or pleasure in activities you normally enjoy, from hobbies to socializing to sex.
- Sleep changes: sleeping too little or too much. Both extremes are common.
- Appetite or weight changes: eating significantly more or less than usual, with noticeable weight gain or loss.
- Fatigue or low energy nearly every day, even without physical exertion.
- Feelings of worthlessness or excessive guilt that go beyond normal self-criticism.
- Difficulty thinking, concentrating, or making decisions.
- Restlessness or feeling physically slowed down, noticeable enough that others can see it.
- Recurrent thoughts of death or suicide, not just a fear of dying but active ideation or planning.
These symptoms need to be present most of the day, nearly every day. A couple of rough days after a stressful event doesn’t meet the threshold. The two-week minimum and the “most of the day” qualifier are what separate clinical depression from ordinary sadness.
Physical Signs You Might Not Expect
Depression is often thought of as a purely emotional condition, but it has a strong physical dimension. Fatigue is one of the most reported symptoms, and it’s not the kind that a good night’s sleep fixes. People describe a heaviness in their body, reduced energy for even basic tasks like showering or cooking, and a general sense of running on empty.
Sleep disruption can go in either direction. Some people develop insomnia, lying awake for hours or waking up too early. Others sleep 10 or more hours and still feel exhausted. Appetite changes can also swing both ways: some people lose all interest in food and drop weight quickly, while others develop intense cravings (often for carbohydrates and comfort foods) and gain weight. Sudden, unexplained shifts in weight are worth paying attention to.
Headaches, back pain, digestive problems, and general body aches are also common. Some people visit their doctor repeatedly for physical complaints without realizing depression is the underlying cause.
How Depression Affects Thinking
The cognitive effects of depression are real and measurable. Depression impairs attention, memory, information processing, and decision-making skills. It also reduces what researchers call cognitive flexibility, your ability to adapt when plans change or situations shift. Executive functioning takes a hit too, making it harder to organize tasks, follow through on multi-step plans, or manage your day.
In practical terms, this looks like rereading the same paragraph five times, staring at a simple decision for 20 minutes, forgetting appointments, or losing track of conversations. At work, it shows up as missed deadlines, trouble focusing in meetings, and withdrawing from coworkers. These cognitive symptoms often get mistaken for laziness or carelessness, which compounds the guilt and shame that depression already brings.
Signs That Look Different in Men
Men experience depression at high rates but tend to express and report it differently. Rather than describing sadness or hopelessness, men are more likely to talk about physical symptoms like fatigue or weight loss. Irritability, anger, and frustration are common presentations, sometimes more prominent than a low mood.
Behavioral changes are also telling. Men with depression may escape into work or exercise compulsively, rely on alcohol or drugs, or start behaving recklessly. These patterns can mask the underlying depression, making it harder for both the person and those around them to recognize what’s happening. Because the stereotype of depression centers on visible sadness and crying, men who express it through anger or withdrawal often go undiagnosed for years.
Signs in Children and Teenagers
Depression in kids looks different from depression in adults. Irritability is often the dominant mood rather than sadness. A child might act out, seem defiant, or lose motivation at school, leading adults to label them as a troublemaker or lazy rather than recognizing depression. Some children don’t talk about feeling hopeless at all. Instead, the signs show up through changes in eating, sleeping, energy, or attention span.
The CDC lists several behaviors commonly seen in children with depression: feeling sad, hopeless, or irritable much of the time; losing interest in fun activities; eating or sleeping significantly more or less than usual; being tired and sluggish or restless and tense; having difficulty paying attention; feeling worthless or guilty; and engaging in self-destructive behavior. Screening for depression is recommended starting at age 12, though symptoms can appear earlier.
Signs in Older Adults
Depression in older adults often gets overlooked because its symptoms overlap with aging or other medical conditions. A phenomenon called pseudodementia is one of the trickiest presentations. It mimics intellectual decline, with forgetfulness, slow movement, low motivation, and mental sluggishness, but the root cause is depression rather than a neurodegenerative condition like Alzheimer’s disease.
One helpful distinction: people with depression-related memory problems tend to notice and worry about their forgetfulness, while people with Alzheimer’s are often indifferent to it. Older adults with depression are also more likely to emphasize physical complaints (pain, fatigue, digestive issues) over emotional ones, which can lead doctors down the wrong diagnostic path if depression isn’t specifically considered.
Atypical Depression Has Its Own Pattern
Not all depression follows the classic pattern of constant low mood. A subtype called atypical depression involves a key feature: mood reactivity. Your mood temporarily lifts in response to something positive, like good news or a fun outing, then drops back down. This can make it easy to dismiss the condition (“See, I was happy at dinner, so I must be fine”).
People with atypical depression also experience at least two of the following: a heavy, leaden feeling in the arms or legs, increased appetite or significant weight gain, excessive sleepiness, and intense sensitivity to rejection or criticism. That last one is especially disruptive. Even imagined or anticipated rejection can trigger strong emotional reactions that interfere with relationships and work.
Depression vs. Grief
Grief and depression can look similar on the surface, but they differ in important ways. Grief centers on the loss of someone or something specific. The sadness comes in waves, often triggered by memories, and self-esteem generally stays intact. The grieving person sees their pain as a natural, expected response to loss.
Depression, by contrast, involves a persistent inability to feel pleasure or anticipate happiness. Instead of focusing on the lost person, the thought patterns turn inward: self-criticism, pessimistic rumination, feelings of worthlessness. Depression is more likely to involve impaired daily functioning, fatigue, excessive sleep, and suicidal thinking than grief alone. That said, grief can trigger a depressive episode, and the two can coexist. If grief doesn’t ease over time and starts producing feelings of worthlessness or hopelessness, that’s a signal something more than normal bereavement is at play.
How Depression Is Screened
The most widely used screening tool is the PHQ-9, a nine-question survey that asks how often you’ve experienced each core symptom over the past two weeks. Each item is scored from 0 (not at all) to 3 (nearly every day), giving a total score between 0 and 27. The scoring breaks down into clear ranges: 0 to 4 is no depression, 5 to 9 is mild, 10 to 14 is moderate, 15 to 19 is moderately severe, and 20 to 27 is severe.
The PHQ-9 is a screening tool, not a diagnosis by itself. But it gives you and a clinician a concrete starting point for conversation. Many primary care offices now use it as part of routine check-ins, and you can find it freely available online to get a sense of where you fall before making an appointment.