One of the mental illnesses he has is Bipolar Disorder.

Bipolar Disorder can cause mania, where you may feel euphoric, energetic, and well rested after only two hours of sleep, and it also causes depression, where you feel too tired to get out of bed, loathe yourself, and feel hopeless. Many people experience the depression even more than the mania, and sometimes manic periods are so mild that they can go by unnoticed. The mood swings aren't super sudden either. You can be in manic or depression for weeks or months.

Bipolar disorder affects not only mood, but energy level, judgement, memory, concentration, appetite, sleep patterns, sex drive, and self esteem.

It is also linked to anxiety, substance abuse, and health problems such as diabetes, heart disease, migraines, and high blood pressure.

Hikaru has this most likely because of not only his past trauma and physical abuse, but also because of his drug abuse.

Some people are more prone to mania than others, while some are more prone to depression. Hikaru is half and half— he'll go through phases where he's he speaks so rapidly people can't keep up, and will be super energetic and sleep very little.

When he's in his depression, he feels hopeless, sad, or empty; sometimes he feels pretty irritable; he can't smile even when he tries, and can't feel happy for himself or anyone else even when he wants to; he's fatigued and non energetic— he's lethargic; he loses his appetite and loses weight; he has trouble sleeping, has trouble concentrating and remembering things, feels guilty and worthless, and, when it's really bad, he thinks about death and suicide a lot.

Seasonal changes can cause his mania or depression. He, like others, tends have mania in the summer, and his depressive episodes kick in during the fall, winter, and spring.

The trigger for his bipolar disorder very well could have been the stress of his home life. It could have been a mix of the abuse and the drugs. It's hard to say for sure.

Not sleeping enough can trigger a manic episode for Hikaru.

Bipolar Symptoms:

~ Manic episodes may include symptoms such as high energy, reduced need for sleep, and loss of touch with reality. Depressive episodes may include symptoms such as low energy, low motivation, and loss of interest in daily activities. Mood episodes last days to months at a time and may also be associated with suicidal thoughts.

Mood:

~ Mood swings
~ Sadness
~ Elevated mood
~ Anger
~ Anxiety
~ Apathy
~ Apprehension
~ Euphoria
~ General discontent
~ Guilt
~ Hopelessness
~ Loss of interest
~ Loss of interest in pleasure or activities

Behavioral:

~ Irritability
~ Risk taking behaviors
~ Disorganized behavior
~ Agression
~ Agitation
~ Crying
~ Excess desire for sex
~ Hyperactivity
~ Impulsivity
~ Restlessness
~ Self-harm

Cognitive:

~ Unwanted thoughts
~ Delusion
~ Lack of concentration
~ Racing thoughts
~ Slowness in activity
~ False belief of superiority

Psychological:

~ Depression
~ Manic episode
~ Agitated depression
~ Paranoia

Weight:

~Weight gain
~ Weight loss

Sleep:

~ Difficultly falling asleep
~ Excess sleepiness

Also Common:

~ Fatigue
~ Rapid and frenzied speaking

Hikaru also has PTSD (Post-traumatic stress disorder).

PTSD, many know what it is. Hikaru has it because of the physical and sexual abuse that he endured. Because of these past events, he'll have nightmares about the events that happened, and he'll wake in a panic attack, believing that it's actually happening because of how real the dream felt. He avoids situations that could cause him to have the "flashbacks" of the traumatic events, such as being alone. He is blind and was deaf at one point, so he also gets frightened if someone unexpectedly touches him and has almost panicked before because it gave him flashbacks.

He often feels anxious or nervous because of all that's happened to him, and part of it is definitely because of the PTSD, which, of course, he got because of the trauma of his past. Sometimes he feels as if he's numb to emotions, too.

Symptoms:

~ Symptoms may include nightmares or unwanted memories of the trauma, avoidance of situations that bring back memories of the trauma, heightened reactions, anxiety, or depressed mood.

Behavioral:

~ Agitation
~ Irritability
~ Hostility
~ Hypervigilance
~ Self-destructive behavior
~ Social isolation

Psychological:

~ Flashback
~ Fear
~ Severe anxiety
~ Mistrust

Mood:

~ Loss of interest or pleasure in activities
~ Guilt
~ Loneliness

Sleep:

~Insonnia
~ Nightmares

Also Common:

~ Emotional detachment
~ Unwanted thoughts

     Another thing Hikaru suffers from is anxiety. It isn't too severe, though, thankfully. It also depends on the situation or on his other disorders.

ADHD:

Attention-deficit/hyperactivity disorder

The symptoms include limited attention and hyperactivity.

Behavioral:

~ Agression
~ Excitability
~ Fidgeting
~ Hyperactivity
~ Impulsivity
~ Irritability
~ Lack of restraint
~ Persistent repetition of words or actions

Cognitive:

~ Absentmindedness
~ Difficulty focusing
~ Forgetfullness
~ Problem paying attention
~ Short attention span

Mood:

~ Anger
~ Anxiety
~ Boredom
~ Excitement
~ Mood swings

Also Common:

~ Depression
~ Learning disability