Normally a dependent totally denies usage. It is only an experienced person who can see signs and recognize dependency and problems.

The chemically dependent person goes through a marked behavioral change in his attitude.

The tell-tale signs are a sudden change of friends, secrecy, lying frequently, stealing, manipulating, borrowing money, selling articles from home, job problems, loss of weight, low appetite, irritation, anger, lethargy, poor personal hygiene, psychological disturbance, lack of concentration, depression, suspicion etc.

These are some of the marked symptoms of the disease.

The signs and symptoms of substance dependence vary according to the individual, the substance they are addicted to, their family history (genetics), and personal circumstances.

The person takes the substance and cannot stop
In many cases, such as nicotine, alcohol or drug dependence, at least one serious attempt was made to give up, but unsuccessfully.
 

Withdrawal symptoms
When body levels of that substance go below a certain level the patient has physical and mood-related symptoms. There are cravings, bouts of moodiness, bad temper, poor focus, a feeling of being depressed and empty, frustration, anger, bitterness and resentment.

There may suddenly be increased appetite. Insomnia is a common symptom of withdrawal. In some cases the individual may have constipation or diarrhea. With some substances, withdrawal can trigger violence, trembling, seizures, hallucinations, and sweats.
 

Addiction continues despite health problem awareness
The individual continues taking the substance regularly, even though they have developed illnesses linked to it. For example, a smoker may continue smoking even after a lung or heart condition develops.
 

Social and/or recreational sacrifices
Some activities are given up because of an addiction to something. For example, an alcoholic may turn down an invitation to go camping or spend a day out on a boat if no alcohol is available, a smoker may decide not to meet up with friends in a smoke-free pub or restaurant.
 

Maintaining a good supply
People who are addicted to a substance will always make sure they have a good supply of it, even if they do not have much money. Sacrifices may be made in the house budget to make sure the substance is as plentiful as possible.
 

Taking risks (1)
In some cases the addicted individual make take risks to make sure he/she can obtain his/her substance, such as stealing or trading sex for money/drugs.
 

Taking risks (2)
While under the influence of some substances the addict may engage in risky activities, such as driving fast.
 

Dealing with problems
An addicted person commonly feels they need their drug to deal with their problems.
 

Obsession
An addicted person may spend more and more time and energy focusing on ways of getting hold of their substance, and in some cases how to use it.
 

Secrecy and solitude
In many cases the addict may take their substance alone, and even in secret.
 

Denial
A significant number of people who are addicted to a substance are in denial. They are not aware (or refuse to acknowledge) that they have a problem.
 

Excess consumption
In some addictions, such as alcohol, some drugs and even nicotine, the individual consumes it to excess. The consequence can be blackouts (cannot remember chunks of time) or physical symptoms, such as a sore throat and bad persistent cough (heavy smokers).
 

Dropping hobbies and activities
As the addiction progresses the individual may stop doing things he/she used to enjoy a lot. This may even be the case with smokers who find they cannot physically cope with taking part in their favorite sport.
 

Having stashes
The addicted individual may have small stocks of their substance hidden away in different parts of the house or car; often in unlikely places.
 

Taking an initial large dose
This is common with alcoholism. The individual may gulp drinks down in order to get drunk and then feel good.
 

Having problems with the law
This is more a characteristic of some drug and alcohol addictions (not nicotine, for example). This may be either because the substance impairs judgment and the individual takes risks they would not take if they were sober, or in order to get hold of the substance they break the law.
 

Financial difficulties
If the substance is expensive the addicted individual may sacrifice a lot to make sure its supply is secured. Even cigarettes, which in some countries, such as the UK, parts of Europe and the USA cost over $11 dollars for a packet of twenty - a 40-a-day smoker in such an area will need to put aside $660 per month, nearly $8,000 per year.
 

Relationship problems
These are more common in drug/alcohol addiction. Some substance/alcohol abusers who are not technically addicted may also suffer from or cause some of the descriptions mentioned above, but they do not usually have the withdrawal symptoms of an addict or the same compulsion to consume the substance.