Most of us feel sad or lonely on occasion. This is a normal response to the trials of life. However, depression is something more significant. It materializes when normal feelings become overwhelming and impact your day-to-day life.

While depression may be more readily accepted and spoken about than it once was, the first signs of depression can still be difficult to identify. Some people hide the early symptoms of depression, or fail to recognize they have them at all.

If you have concerns for yourself or a loved one, it can be comforting to know which early symptoms of depression to look for, whether they show up on their own or as part of a larger pattern. Here are the twelve first signs of depression that you should watch out for:

Sign #1: Loss of Concentration

While loss of concentration can easily be attributed to many factors, it can be one of the first signs of depression. Whether you have trouble remembering details or difficulty making a decision, a change in your ability to concentrate can be a warning sign that you should think about other symptoms, and whether or not it is part of a pattern.

Sign #2: Fatigue

Although fatigue can be linked to a wide range of health issues, this is among the first signs of depression. This is particularly true if your sleeping, eating and exercise habits have remained stable, but you suddenly feel fatigued throughout the day.

Sign #3: Pessimism and Feelings of Hopelessness

If you suffer from early symptoms of depression, you may have trouble seeing the future the way others do. You may feel less optimistic than those around you; many also struggle with feelings of hopelessness and a general lack of control.

Sign #4: Sleep Challenges

Sleeplessness is an early symptom of depression that tends to form a vicious cycle. While a lack of sleep can contribute to depression, depression itself can make it more difficult to sleep.

Sometimes, this materializes in the early morning, waking you up long before you intended or wanted. Conversely, if you find yourself suddenly sleeping far more than you have, you may also be exhibiting a symptom of depression.

Sign #5: Irritable or Angry Behaviour

Not everyone knows that depression can show up as irritability or anger, but mood changes can be an early symptom or sign of depression. If you or a loved one find yourself losing patience for things that were once tolerated more easily, depression may be the cause.

Sign #6: Feelings of Guilt or Worthlessness

Everyone feels guilty at some point, but feelings that extend to worthlessness should be taken as a red flag. If you struggle to see how you can change your situation, or if you have feelings of helplessness, be aware that these can be signs of depression.

Sign #7: Hobbies No Longer Hold Your Interest

A sudden disinterest in hobbies, or activities that once brought you pleasure, can be a telltale sign of depression. If you can’t get yourself to feel the way you once did about your hobbies—whether individual or group activities—consider it a warning sign of depression.

Sign #8: Changes to Weight or Appetite

The first signs of depression can materialize in the food you eat, as well. If you have weight gain, caused by over-eating for comfort or relief of anxiety, or weight loss due to a lack of appetite, keep in mind that depression could be one of the root causes.

Sign #9: Physical Pains

The early symptoms of depression can materialize in physical ways as well. Although it is often tricky to diagnose pain related to depression, it can appear as persistent aches, pains, cramps or headaches.

Sign #10: Health Disorders

Another physical sign that can be difficult to connect to depression is the appearance of one or more health disorders. Research shows that people with depression are more likely to experience digestive problems, heart disease, arthritis, type 2 diabetes and certain autoimmune disorders.

While it is difficult to determine which issue causes the other, keep in mind that if you suffer from one of these conditions, you may also have depression.

Sign #11: Low Sex Drive

Whether alone or in conjunction with other symptoms, a low or suddenly reduced sex drive can be directly linked to depression. If you noticed a low sex drive, this could be a possible sign or symptom of depression.

Sign #12: Artificial Happiness

Some people, aware of their depression, try to mask their struggle with an artificial sense of well-being. This can manifest in artificial smiles or generally pretending to be happy, in hopes that it will help. If this is something you know you do—pretend to be happy, in order to hide your real feelings, consider it a warning sign.

The first signs of depression can be tricky to identify. Often masked as simple changes to your life or well-being, they can be easily ignored. If you find yourself with a handful or a cluster of symptoms, or a general sense that all is not as it should be, consider seeking mental health services to determine the next steps. Depression is a common issue for many, but not something that should be endured alone.