"Having down days is a perfectly normal part of human nature, and usually these feelings will pass without having any major impact on your life.
"But if the feelings don't go away after a couple of weeks, get worse or keep returning, and you no longer enjoy things you normally would, it could be a sign that you're experiencing depression," she told The Independent.
2. You are having trouble concentrating
You might have difficulty thinking and speaking clearly and have problems with your concentration levels and memory.
"If you find your concentration is worse than usual, or that you're having trouble with things like punctuality and decision-making at work or school, this might be a symptom of living with a mental health problem," she said.
3. You are having problems with sleep
If you are having difficulty getting up in the morning and sleep excessively, it could be a sign of depression or anxiety.
Problems getting to sleep at night could also be a symptom of poor mental health.
"There is a close relationship between sleep and mental health, and sleep deprivation can also make your mental health worse," she said.
4. You feel detached or numb
Depression and anxiety could give you what Lyus describes as "a sense of unreality," making it hard for you to connect to everything going on around you.
"For example, you might be sitting in a meeting at work and find it difficult to keep up with what people are saying, or feel as though you're not really there", she said.
5. You have physical symptoms
Depression and anxiety might cause you to sweat and shake and feel nauseous. You may even have a panic attack.
It may also affect your diet, stopping you eating as well as you did, and you may start neglecting your personal hygiene.
Almost two-thirds of people in the UK have suffered from a mental health problem according to a study commissioned by the Mental Health Foundation.
Research that lays bare the growing problem of mental ill-health to an NHS buckling under huge patient demand found that seven in 10 women, young adults aged 18-34 and people living alone had also experienced a mental health problem at some time in their lives.
Only 13% of people were found to be living with high levels of good mental health.
More than four in 10 people said they had suffered from depression and over a quarter had experienced panic attacks.
The study, in which 2,290 people were interviewed online and over the phone in England, Scotland and Wales, linked poor mental health with low income and unemployment.
Almost three in four people living in the lowest household incomes said they had suffered a mental health problem compared with six in 10 people in the highest income households.
Eighty-five percent of those unemployed experienced a mental health problem compared with two-thirds of working people and just over half of retired people. Better mental health was seen in people over 55.
"People aged 55 and above are the most likely to take positive steps to help themselves deal better with everyday life - including spending time with friends and family, going for a walk, spending more time on interests, getting enough sleep, eating healthily and learning new things," said the report, "Surviving or Thriving? The state of the UK's mental health."
The research carried out by NatCen on behalf of the Mental Health Foundation.
