what is a study where you try to observe subjects in a natural environment

Depression:

Feelings of sadness, tearfulness, emptiness, and hopelessnessFeelings of worthlessness or guilt, fixating on past failures or self-blameLoss of interest or pleasure in most or all normal activitiesNot being able to sleep or sleeping too much.Tiredness and lack of energy, so even small tasks take extra effort

Anorexia Nervosa:

Extreme weight loss or not making expected developmental weight gainsThin appearanceInability to retain heatFatigueEroded teeth due to (induced) vomitingDizziness or fainting

Bulimia Nervosa:

Living in fear of gaining weightFeeling a loss of control during bingeing — like you can't stop eating or can't control what you eatForcing yourself to vomit or exercising too much to keep from gaining weight after bingeingUsing laxatives, diuretics, enemas after eating when they're not neededFasting, restricting calories, avoiding certain foods between binges

Binge Eating Disorder

Eating unusually large amounts of food in a specific amount of timeEating even when you're full or not hungryFrequently eating alone or in secretFeeling depressed, disgusted, ashamed, guilty, or upset about your eatingFrequently dieting, possibly without weight loss

(sources: WebMD, Mayo Clinic)

depression:

-Lack of focus, poor self esteem, suicidal thoughts/actions, can't sleep, doesn't participate in anything, anxiety, etc.

anorexia nervosa:

-feeling fainting, can't sleep, anxiety, feeling guilty, constantly judging yourself, negative thoughts about body, etc.

bulimia nervosa :

-mood swings, anxiety, can't sleep, negative thoughts about body, guilt, etc.

binge eating disorder :

-Having no control over the amount of food you eat, a constant feeling to keep eating, anxiety about weight, depression, poor self esteem, etc.

hope this helps!!!